Download Shakuntala-Devi-Puzzles with SOlutions PDF Below Read More

For problems 1-4, replace the ? in each series of numbers with the most appropriate number. 1. 18, 14, 12, 11, ?, 10.25 Answer 2. 11, 12, 26, 79, 81, 163, 491, 492, ? Answer 3. 4, 1.33, 4.17, 1.39, 4.36, 1.45, ? ... Read More

Puzzle Set 001 1. Two people were walking in opposite directions.both of them walked 6 miles forward then took right and walked 8 miles.how far is each from starting positions? a) 14 miles... Read More

Lateral Thinking Puzzles   lll ... Read More

If you think you know any of the answers please specify below the question number you are answering and what you think the answer is. Where can anybody but you sit? Why would a cleaning person prefer to wash a mirror than a window of... Read More

This was a burglary in the Silver City jewelry store last Sunday. Three suspects: Robert,... Read More

A fast train leaves London for Brighton and at the same time a slow train leaves Brighton for London. The fast train leaves at 80 mph and the slow train travels at 35 mph. When they meet, which is farther from London? ... Read More

Classic: If a bear walks one mile south, turns left and walks one mile to the east and then turns left again and walks one mile north and arrives at its original position, what is the color of the bear. ANS. The color of the bear is trivial. The... Read More

The Puzzle: A girl, a boy, and a dog start walking down a road. They start at the same time, from the same point, in the same direction. The boy walks at 5 km/h, the girl at 6 km/h. The dog runs from boy to girl and back again with a constant... Read More

Eight eggs look identical except one is lighter. How can you weigh only 2 times on a balance... Read More

My intention here is not to trouble Google interviewers. I was just collecting some classic puzzles and found this one and a small Google search showed me that this is a Google interview puzzle to my pleasant surprise. But many of the answers I found... Read More

Visual Puzzle Set 001 1. This one means Breakfast now figure out the rest 2. 3. 4. 5. 6. 7. ... Read More

There were 2 tribes living on an island. The east tribal people always tell a lie. The west... Read More

Brain Teaser Try to get 56 in all the red boxes, using the pull-down lists! ... Read More

The Puzzle: Three friends have a nice meal together, and the bill is $25 The three friends pay $10 each, which the waiter gives to the Cashier The Cashier hands back $5 to the Waiter But the Waiter can’t split $5 three ways, so he gives the... Read More

The Handshake Problem At a party, everyone shook hands with everybody else. There were 66 handshakes. How many people were at the party? Answer: Handshakes are used traditionally as greetings, but they are also used to seal an agreement... Read More

Jimmie Dean visited an island. There were 2 tribes... Read More

As shown in the figure, each letter represents a distinct digit. What are A, B, C, and D? ... Read More

Here are a dozen more free brain teasers for you. Scroll down for the solutions. 1. A woman tries to drop her husband into the ocean, but he blows back into the boat. Why? 2. A man wakes up and sees that his brother is dead. Though... Read More

In this post I want to describe about a series of puzzles called weighing puzzles. These puzzle vary in hardness from simple to extremely mathematical involving either expertise in some fields or extreme ingenuity. Either you know it or you figure... Read More

This is not one of the classic Microsoft puzzle. I recently heard from a friend. I am listing the problem below. There is a table on which a number of coins are placed. You also know that there are as many coins with Head up as many coins... Read More

I have a horse. Do you know what color it is Allan said, "I guess it is not... Read More

A lady and a gentleman are sister and brother. We do not know who is older. ... Read More

12 Balls Problem This is a beautifully simple puzzle which was first brought to my attention in the letters section of the Daily Telegraph on February 7, 2003. Mr Harold Hopwood wrote: "Sir - Many years ago, a maths lecturer put to me the... Read More

The Puzzle: You have three bowls: 7, 4 and 3 liters in capacity. Only the 7-liter is full. Pour the fewest times to have the bowls containing 2, 2 and 3 liters. . . . . (Scroll down if you really want to see the Solution... Read More

The Puzzle: When asked about his birthday, a man said: "The day before yesterday I was only 25 and next year I will turn 28." This is true only one day in a year - when was he born? . . . . (Scroll down if you really want ... Read More

The Puzzle: The following equation is wrong: 101 - 102 = 1 Move one numeral to make it correct. (Caution: Trick) . . . . (Scroll down if you really want to see the Solution ...) . . . . . . The... Read More

All 3 boxes with labels are COMPLETELY mislabeled. You will be allowed to take only one... Read More

Puzzle Set 002 1. Brothers and sisters have I none, but that man’s father is my father’s son. Who is that man? 2. What is the simplest way in which two people can be an... Read More

Classic Brain Teasers Riddles 1. A woman proves in court that her husband was murdered by her sister, but the judge decides that the sister cannot be punished. Why? 2. A woman is found hanging by her neck from the high... Read More

BRAINBENDER PUZZLES   Puzzle 1 ... Read More

Create New Jokes Writing a new joke is difficult, and can be both systematic and creative. This makes it a great mind puzzle. Just start with a word or a subject, and find a new way to make a joke about it. I’ll start with ... Read More

The World’s Hardest Riddle? Some have claimed this to be the worlds hardest riddle. It isn’t. It is a decent riddle, though, and a fun one for those who like riddles with systematic solutions. My own solution is below.... Read More

A six digit number 312132 has two 1’s, two 2’s and two 3’s. This number... Read More

One extra coin Player A has one more coin than player B.  Both players throw all of their coins simultaneously and observe the number that come up heads.  Assuming all the coins are fair, what is the probability that A obtains more heads... Read More

Sum of two powers 2  If x and y are positive real numbers, show that xy + yx > 1. Solution to puzzle : Sum of two powers 2 If x and y are positive real numbers, show that xy + yx > 1. Suppose x 1. Then xy 1 and yx > 0. ... Read More

There are 3 triplet brothers. They look identical.... Read More

Grammar Problem Can you make the words below into grammatically correct English simply by adding punctuation? You may not change the word order, or add or remove any words. You may replace lower case with upper case letters. You can click and drag... Read More

Among 6 coins one is heavier than all the others. You can weigh only 2 times to find out... Read More

Farmer’s enclosure A farmer has four straight pieces of fencing: 1, 2, 3, and 4 yards in length.  What is the maximum area he can enclose by connecting the pieces?  Assume the land is flat. Solution to puzzle : Farmer’s... Read More

Area of a rhombus  A rhombus, ABCD, has sides of length 10.  A circle with center A passes through C (the opposite vertex.)  Likewise, a circle with center B passes through D.  If the two circles are tangent to each... Read More

The Bacteriologist Problem - part 1   A scientist is experimenting with bacteria that are one micron in diameter and that reproduce by dividing every minute into two bacteria. At 12:00 PM, she puts a single organism in a container.... Read More

The Eye Puzzle The rectangle of colored dots is actually a stereogram. In order to visualize the three-dimensional image, you need to focus about 3 inches (7.5 cm) above of the plane of the computer screen. (Hint: Look at the tip of your... Read More

MNC Puzzle Questions and Answers    1.  A boy multiplied a number with 10 and got 100. If he divided it by 10, what would be the answer?  Answer is 1    2. If a 12 shell cupboard requires 18 ft of wall space then how... Read More

The Rope Bridge Four people need to cross a rickety rope bridge to get back to their camp at night. Unfortunately, they only have one flashlight and it only has enough light left... Read More

1.With how few assistants can an intrepid explorer make a 6 day crossing on foot of an absolutelybarren desert, if he and the available assistants can each carry only enough food and water to last one man four days? Look for the simplest humane soln.... Read More

The Puzzle: You have eight bags, each of them containing 48 coins. Five of these bags contain only true coins, the rest of them contain fake coins. Fake coins weigh 1 gram less than the real coins. You do not know what bags have fake coins and... Read More

Mind Puzzles Mind puzzles can be simple math or number problems, like the following. 1. Find the next number in the series: 1...2...5...14...41...122...? You’ll find the answer further down. They can also be lateral... Read More

The Poisons Problem Hydrochloric acid is a corrosive, fuming, poisonous, highly acidic solution of hydrogen chloride (HCl). Sodium hydroxide is a caustic, strongly alkaline compound (NaOH) used in drain cleaners. If ingested, hydrochloric acid... Read More

Fill in numbers 1, 2, 3, 4, 5, 6, 7, 8 and 9 into... Read More

Can you draw the figure as shown in one stroke? Your pen or pencil can not leave the paper... Read More

10 matches made 3 squares as shown. Can you jsut move 1 match to make 4 rectangles? ... Read More

1.There is a game which is being played by 2 persons A and B. The 2 players start the game keeping identical 50 paise coins on a blank board alternately. The 50 paise coins can be kept in the board such that no part of the coin is outside... Read More

500 men were arranged in 10 rows and 50 columns. They picked the oldest person from each row and the tallest of these persons is ’A’. They replace them in their places and again picked tallest person... Read More

Two men and two women stand on a riverbank. They would like to get on the other side with a boat. Unfortunately, the boat can only carry as much as two people. The 4 people can not cross the river at the same speed. One women is able to cross it in... Read More

Puzzle Set 004 1. Three people check into a hotel. They pay $30 to the manager and go to their room. The manager finds out that the room rate is $25 and gives $5 to the bellboy to return. On the... Read More

271 Write 271 as the sum of positive real numbers so as to maximize their product. Solution to puzzle: 271 Write 271 as the sum of positive real numbers so as to maximize their product. Solution 1 Firstly, we note that, to maximize the product,... Read More

The Puzzle: There are nine compositions (A to I) of eight colored cubes. Find two identical compositions. They can be rotated. Author: Peter Grabarchuk This Puzzle © 2008 Peter Grabarchuk. All Rights Reserved. More from Peter Grabarchuk... Read More

The Puzzle: 5 pirates of different ages have a treasure of 100 gold coins. On their ship, they decide to split the coins using this scheme: The oldest pirate proposes how to share the coins, and all pirates remaining will vote for or against it. ... Read More

The Puzzle: Two boys wish to cross a river. The only way to get to the other side is by boat, but that boat can only take one boy at a time. The boat cannot return on its own, there are no ropes or similar tricks, yet both boys manage to cross using... Read More

The Puzzle: What mathematical symbol can be put between 5 and 9, to get a number bigger than 5 and smaller than 9? (Caution: Trick) . . . . (Scroll down if you really want to see the Solution ...) . . . . . ... Read More

QUS: There is a prisoner who is about to... Read More

15 matches make a figure as shown. Can you remove 3 matches to make 3 squares with the same... Read More

17 matches make a figure as shown. Can you remove 5 matches to make 3 squares with the same... Read More

16 matches made 5 squares as shown. Move 2 matches to make 4 squares. One of the squares... Read More

You go to... Read More

Puzzle Set 005 1. Next door to me are 4 brothers of different heights. Their average height is 74 inches and the difference among height of the first three men is 2 inches. The difference between... Read More

The Puzzle: Two fathers took their sons fishing. Each man and son caught one fish, but when they returned to camp there were only 3 fish. How could this be? (None of the fish were eaten, lost, or thrown back.) . . . . (Scroll... Read More

The Puzzle: Using the numerals 1,7,7,7 and 7 (a "1" and four "7"s) create the number 100. As well as the five numerals you can use the usual mathematical operations +, -, x, ÷ and brackets (). For example: (7+1) × (7+7) = 112 would be a good... Read More

The Puzzle: How can I get the answer 24 by only using the numbers 8,8,3,3. You can use the main signs add, subtract multiply and divide. (Puzzle supplied by "Steve123") . . . . (Scroll down if you really want to see the... Read More

The Puzzle: I am thinking of a 6-digit number. The sum of the digits is 43. And only two of the following three statements about the number are true: (1) it’s a square number, (2) it’s a cube number, and (3) the number is under 500000... Read More

Can you cut the board into 3 pieces along the dashed lines... Read More

The math teacher said to his students: “Learn-Practice And Learn-Practice. Keep learning,... Read More

Five card trick Two information theoreticians, A and B, perform a trick with a shuffled deck of cards, jokers removed.  A asks a member of the audience to select five cards at random from the deck.  The audience member passes the five cards... Read More

The Puzzle: Joey leaves his house in the morning to go to day camp. Just as he is leaving his house he looks at an analog clock reflected in the mirror. There are no numbers on the clock, so Joey makes an error in reading the time since it is a... Read More

The Puzzle: If one and a half hens lay one and a half eggs in one and a half days, how many eggs does one hen lay in one day? . . . . (Scroll down if you really want to see the Solution ...) . . . . . . ... Read More

The Puzzle: A Teacher thinks of two consecutive numbers in the range 1 to 10, and tells Alex one of the numbers and Sam the other. Sam and Alex have the following conversation: Alex: I don’t know your number. Sam: I don’t know your... Read More

There was a burglary in the Silver City jewelry store again on Tuesday. A famous jewel was... Read More

The figure shown is a 9 by 16 rectangle. Cut the rectangle into 2 pieces, each of the same... Read More

There are 16 chips laid out as a ‘T’ shape as shown in the figure. Notice if we... Read More

A man covered 28 steps in 30 seconds but he decided to move fast and covered 34 steps in 18 seconds. How many steps are there on the escalator when stationary. All fair skinned, rich, handsome, muscular, lean and employed are... Read More

The Puzzle: You have a full bucket containing 24 liters of liquid. You also have three empty buckets: one of 5 liters, one of 11 liters, and one of 13 liters. How could you divide the 24 liters of liquid into three equal parts, so that you have... Read More

The Puzzle: You have a mobile with a keyboard which consists of 10 digits and two symbols, [#] and [*], as shown in the illustration. On the mobile’s screen is a small program which shows the same keyboard, but with the buttons in a different... Read More

The Puzzle: The school children were returning to their homes when they met the mathematical milkman, who propounds the following problem: In one of the two cans there is milk which is so rich with cream that it becomes... Read More

Ant on a box  A 12 by 25 by 36 cm cereal box is lying on the floor on one of its 25 by 36 cm faces.  An ant, located at one of the bottom corners of the box, must crawl along the outside of the box to reach the opposite bottom corner.... Read More

The Puzzle: A solid, four-inch cube of wood is coated with blue paint on all six sides. Then the cube is cut into smaller one-inch cubes. These new one-inch cubes will have either three blue sides, two blue sides, one blue side, or no blue sides.... Read More

The Puzzle: On your travels you come to an old man on the side of the road holding three cards from a standard deck face down. Trying to make conversation you ask him what the three cards are. He tells you, "To the left of the queen, are one or two... Read More

The Puzzle: There are 2 trees in a garden (tree "A" and "B") and on the both trees are some birds. The birds of tree A say to the birds of tree B that if one of you comes to our tree, then our population will be the double of yours. Then the... Read More

29 matches made a figure as shown. Can you remove 6 matches to make 6 squares with the same... Read More

There are 4 red and blue chips in a 16-square board. Can you rearrange them in such a way... Read More

A and C are single digit numbers. To make the equation as shown, what should A and C be? ... Read More

The Puzzle: A pool has four taps. The first tap takes two days to fill the pool, the second tap three days, the third four days and the last one only 6 hours. How long will it take to fill the pool using all 4 taps at once? . . . ... Read More

The Puzzle: What 5-digit number has the following features: If we put the numeral 1 at the beginning, we get a number three times smaller than if we put the numeral 1 at the end of the number. . . . . (Scroll down if you... Read More

The Puzzle: 5 people are standing in a queue for plane tickets in Germany; each one has a name, an age, a favourite TV program, where they live, a hairstyle and a destination. Names: Bob, Keeley, Rachael, Eilish and Amy TV programs: the Simpsons,... Read More

The Chicken and Egg Problem A chicken farmer has figured out that a hen and a half can lay an egg and a half in a day and a half. How many hens does the farmer need to produce one dozen eggs in six days? Answer: This is a classic problem... Read More

18 matches made 6 small triangles and 2 large triangles. Please move 6 matches to make 6... Read More

There are 7 small squares made of 20 matches. Move 3 matches to make 5 equal squares ... Read More

13 matches make a figure as shown. Can you move 2 matches to make 6 triangles with the same... Read More

Lateral Thinking Puzzles Set 001     ... Read More

Five marbles Five marbles of various sizes are placed in a conical funnel.  Each marble is in contact with the adjacent marble(s).  Also, each marble is in contact all around the funnel wall. The smallest marble has a radius of 8mm. ... Read More

The Puzzle: You have to do an experiment to determine the highest floor on a 100-floor building from which a manufactured snooker ball may be dropped without breaking. You are given two identical snooker balls, which you can drop from various... Read More

The Puzzle: A popular mathematical passtime: Use exactly four 4’s to form every integer from 0 to 50, using only the operators +, -, x, /, () (brackets) x2 (square), and ! (factorial). Example: 0 = 44-44 . . . . (Scroll... Read More

The Problem: A census taker approaches a house and asks the woman who answers the door,"How many children do you have, and what are their ages?" Woman: "I have three... Read More

I visited my math teacher last February. My teacher told me there were 3 groups of students... Read More

The area ABC is 40 square feet. The length of the line segment BD is 1/4 of the line segment... Read More

The curve is composed by connecting 6 quarter circumferences with different sizes as shown... Read More

9 matches made a triangle as shown in the figure, Can you move 3 matches to make the new... Read More

Knowledge Base - Learn more facts to energize your brain Characteristic of number 37 If we multiply 37 by 3, we will get 111. Factors: (The number can... Read More

Confused bank teller  A confused bank teller transposed the dollars and cents when he cashed a check for Ms Smith, giving her dollars instead of cents and cents instead of dollars.  After buying a newspaper for 50 cents, Ms Smith... Read More

Five men, a monkey, and some coconuts Five men crash-land their airplane on a deserted island in the South Pacific.  On their first day they gather as many coconuts as they can find into one big pile.  They decide that, since it is getting... Read More

The Puzzle: In front of you are several long fuses. You know they burn for exactly one hour after you light them at one end. The entire fuse does not necessarily burn at a constant speed. For example, it might take five minutes to burn through half... Read More

The Puzzle: There are three people (Alex, Brook and Cody), one of whom is a knight, one a knave, and one a spy. The knight always tells the truth, the knave always lies, and the spy can either lie or tell the truth. Alex says: "Cody is a knave."... Read More

The Puzzle: A man has four cards in his hand facing him, from 2 to 5. He wants them placed in ascending order from his left to his right. To do this, he takes the leftmost card (from your perspective) and puts it last. He then takes the third card... Read More

The Puzzle: Solve the following: (L+O+G+I+C)3= LOGIC . . . . (Scroll down if you really want to see the Solution ...) . . . . . . The Solution . . . (1+9+6+8+3)3= 19683 Read More

Of course problem 1 can be solved simply by trying some different numbers However, if we want to solve problem 2 it is a bit more tricky. What we will do here is show how to solve the first problem using... Read More

The Bacteriologist Problem - part 2   A scientist is experimenting with bacteria that are one micron in diameter and that reproduce by dividing every minute into two bacteria. At 12:00 PM, she puts a single organism in a container.... Read More

It is said that Galileo (1564-1642) dropped balls of various weights from the top of the Leaning Tower of Pisa to refute an Aristotelian belief that heavier objects fall faster than lighter objects. If the balls were dropped from a... Read More

12 matches made a figures as shown. Move 3 matches to make 3 squares Puzzle... Read More

12 matches make 4 squares as shown. Move 2 matches to make 6 squares Puzzle... Read More

Cards are there. U have to arrange them in a 3*3 matrix. Cards are of 4 colors.they are red,yellow,blue,green. Conditions for arrangement: one red card must be in first row Or second row.2 green cards... Read More

Crazy dice Roll a standard pair of six-sided dice, and note the sum.  There is one way of obtaining a 2, two ways of obtaining a 3, and so on, up to one way of obtaining a 12.  Find all other pairs of six-sided dice such that... Read More

The Puzzle: There are five squares (one 3x3 and four 1x1) formed with 20 matchsticks, as shown in the illustration. Move two matchstick to get seven squares. Overlapping or breaking of matchsticks or "loose ends" are not allowed. Author: Peter... Read More

The Puzzle: If it were two hours later, it would be half as long until midnight as it would be if it were an hour later. What time is it now? . . . . (Scroll down if you really want to see the Solution ...) . . . ... Read More

The Puzzle: You have nine circles (divided into 16 smaller sectors). Each has a different pattern of holes. Which two of them can form an opaque (non-transparent) circle when stacked on top of each other? Circles can be rotated and/or overturned. ... Read More

The Puzzle: You have 9 balls, equally big, equally heavy - except for one, which is a little heavier. How would you identify the heavier ball if you could use a pair of balance scales only twice? . . . . (Scroll down if you... Read More

The Puzzle: Cannibals ambush a safari in the jungle and capture three men. The cannibals give the men a single chance to escape uneaten. The captives are lined up in order of height, and are tied to stakes. The man in the rear can see the backs of... Read More

The Puzzle: There are three people (Alex, Brook and Cody), one of whom is a knight, one a knave, and one a spy. The knight always tells the truth, the knave always lies, and the spy can either lie or tell the truth. They are brought before a... Read More

The Puzzle: Can you arrange the numerals 1 to 9 (1, 2, 3, 4, 5, 6, 7, 8 and 9) in a single fraction that equals exactly 1/3 (one third)? Example that doesn’t work: 7192/38456 = 0.187 . . . . (Scroll down if you really... Read More

The Puzzle: Two friends have a nice meal together, and the bill is $25 The friends pay $15 each, which the Waiter gives to the Cashier The Cashier hands back $5 to the Waiter The Waiter keeps $3 as a tip and hands back $1 each So, the friends... Read More

The Puzzle: There are 5 ships in a port: 1. The Greek ship leaves at six and carries coffee. 2. The Ship in the middle has a black chimney. 3. The English ship leaves at nine. 4. The French ship with blue chimney is to the left of a ship that... Read More

The Puzzle: When they started off on the great annual picnic every wagon in town was pressed into service. Half way to the picnic ground ten wagons broke down, so it was necessary for each of the remaining wagons to carry one... Read More

The Puzzle: Aesop tells how a father and son failing to ride their donkey in a way to please the public, finally decided to carry the beast. They had not gone far, however, when they met the village schoolmaster, who explained that... Read More

The Numerology Problem Can you figure out the special significance of the following sequence?   (2, 6, 10, 15, 19) Answer: The words "Numerology" and "special significance" in the statement of the problem should have given you a... Read More

  A valuable painting was stolen from the Liar’s Club, but the police are having a hard time identifying the culprit because every statement made by a member of the Liar’s Club is false. Only four members visited the club ... Read More

One of the most classic puzzles involving balls is figuring out the odd one out using common balance.There are many levels of puzzles based on the same concept for different levels of interviews - Simple ones for phone interviews to the most... Read More

Place the alphabets A to I into the 3 x 3 box. E is to the right of C. A is to the right... Read More

Two quarter circles tangent each other within the square ABCD. Assume the radius of the... Read More

Can you cut the board into 4 pieces along with the dashed lines so each piece has the same... Read More

12 matches made 4 squares as shown in the figure. 1. Move 3 matches to make 3... Read More

18 matches make 6 squares as shown. Remove 2 matches first to make 5 squares and then move 2... Read More

Fill in the 9 numbers: 1, 2, 3, 4, 5, 6, 7, 8, 9... Read More

Fill in numbers 1, 2, 3, 4, 5, 6, 7, 8 and 9 into... Read More

Can you plug in either addition(+), subtraction(-), multiplication(x), division(/) and... Read More

Switches This one was recently given on Car Talk, and it’s been making the rounds right now also... The warden meets with 23 new prisoners when they arrive. He... Read More

Puzzle Set 007 1. Fifty minutes ago if it was four times as many minutes past three o,clock,how many minutes is it to six o,clock? 2. What is the next number in the series 10... Read More

Coin triplets Two players play the following game with a fair coin.  Player 1 chooses (and announces) a triplet (HHH, HHT, HTH, HTT, THH, THT, TTH, or TTT) that might result from three successive tosses of the coin.  Player 2 then chooses a... Read More

The Puzzle: Measure exactly 2 liters of water if you have: 1) 4 and 5-liter bowls 2) 4 and 3-liter bowls . . . . (Scroll down if you really want to see the Solution ...) . . . . . . The Solution . . .... Read More

The Puzzle: You are doing some gardening, and need exactly 4 liters of water to mix up some special formula for your award winning roses. But you only have a 5-liter and a 3-liter bowl, but do have access to plenty of water. How would you measure... Read More

The Puzzle: One of twelve pool balls is a bit lighter or heavier (you do not know) than the others. At least how many times do you have to use an old balance-type pair of scales to identify this ball? . . . . (Scroll down if... Read More

The Puzzle: Six coins make the Triangle Man shown in the illustration. The coins form three identical equilateral triangles as shown with the dotted lines. Rearrange the coins into another shape with three equilateral triangles, each with a... Read More

The Puzzle: You have a basket containing ten apples. You have ten friends, who each desire an apple. You give each of your friends one apple. After a few minutes each of your friends has one apple each, yet there is an apple remaining in the basket.... Read More

The Puzzle: At a restaurant downtown, Mr. Red, Mr. Blue, and Mr. White meet for lunch. Under their coats they are wearing either a red, blue, or white shirt. Mr. Blue says, "Hey, did you notice we are all wearing different colored shirts from our... Read More

The Puzzle: Here is a puzzle known as the Covent Garden Problem, which appeared in London half a century ago, accompanied by the somewhat surprising assertion that it had mystified the best mathematicians of England: Mrs.... Read More

The Puzzle: Charlie and Freddie, having sent their lingerie consisting of thirty pieces to the wash, Freddie calls for the same and explains that as his bundle contains half of the cuffs and but one-third of the collars, it should... Read More

The Puzzle: This odd little problem in domestic arithmetic was sprung by the cook upon Mrs. Smith when she wanted to know what the grocer charged for such small eggs. "I paid twelve cents for the lot," replied Bridget, "but I... Read More

The Puzzle: Solve the following: COW × COW = DEDCOW . . . . (Scroll down if you really want to see the Solution ...) . . . . . . The Solution . . . 376 × 376=141376 Read More

The Problem: A man has to get a fox, a chicken, and a sack of corn across a river. He has a rowboat, and it can only carry him and one... Read More

One of the most asked and well known microsoft interview question is that of the walking bear.The question is still asked because a lot of people have either not heard of it or most of them don't know the correct solution yet. If a... Read More

Alphabets A through R are printed above the box,... Read More

There was a burglary in the Silver City jewelry store again on Monday. Three suspects:... Read More

Take a pencil and duplicate the figure in a continuous line. The pencil can not leave the... Read More

24 matches made a figure as shown. Can you remove 4 pieces of matches to make 5 squares with... Read More

Folded sheet of paper A rectangular sheet of paper is folded so that two diagonally opposite corners come together.  If the crease formed is the same length as the longer side of the sheet, what is the ratio of the longer side of the sheet to... Read More

Three children  On the first day of a new job, a colleague invites you around for a barbecue.  As the two of you arrive at his home, a young boy throws open the door to welcome his father.  “My other two kids will be home soon!”... Read More

No consecutive heads A fair coin is tossed n times.  What is the probability that no two consecutive heads appear? Solution to puzzle : No consecutive heads A fair coin is tossed n times.  What is the probability that no two consecutive... Read More

he Puzzle: Imagine having three bowls, with the following capacities: In bowl A (8 liters capacity) are 5 liters of water. In bowl B (5 liters capacity) are 3 liters of water. In bowl C (3 liters capacity) are 2 liters of water. Can you measure... Read More

The Puzzle: A Man carries his son into the hospital because his son has a nail in his foot. The Surgeon then walks in and says "I cannot operate on this boy … he is my son". What is going on here? . . . . (Scroll down if you... Read More

The Puzzle: A man walks into a bar and asks the bartender for a glass of water. But the bartender takes out a gun and aims it at the man’s head. The man says "Thank You" and walks out. Why? . . . . (Scroll down if... Read More

The Puzzle: Eight married couples meet to lend one another some books. Couples have the same surname, employment and car. Each couple has a favourite colour. Furthermore we know the following facts: 1. Daniella Black and her husband work as Shop... Read More

The Puzzle: Bluebeard explains that his bunch of keys was strung upon an endless key ring and divided into three groups so that the first group multiplied by the second equaled the third! That was the secret by which he knew... Read More

The Puzzle: Solve the following: CL=LOGIC . . . . (Scroll down if you really want to see the Solution ...) . . . . . . The Solution . . . 57=78125 Read More

The Missing Dollar Problem Three students checked into a hotel and paid the clerk $30 for a room ($10 each). When the hotel manager returned, he noticed that the clerk had incorrectly charged $30 instead of $25 for the room. The manager told... Read More

The Mathematics Class Problem All students in the physics class also study mathematics. Half of those who study literature also study mathematics. Half of the students in the mathematics class study physics. Thirty students study literature... Read More

The Ship in a Tub Problem - part 2 A toy ship is floating in a cylindrical container 10 centimeters in diameter that is partially filled with water. If a silver teddy bear weighing 100 grams falls off the ship and sinks to the bottom of the... Read More

This is a very common interview puzzle. The problem is very simple if you understand it. So the point to note is, do not arrive at the solution so "fast”, if you are asked this puzzle in an interview and if you are not planning to show any... Read More

There are 2 pitchers you can use to get 4 pints of water from a brook. One is 10 pints and... Read More

The pharmacy has an old scale which has only two measuring weights 30 grams and 5 grams. How... Read More

In this figure, which area is larger, Area 1 or Area 5? How much is the difference? ... Read More

There are 4 identical 3-ring chains. How many rings do you have to cut off in order to re... Read More

18 matches made 6 small triangles and 2 large triangles as shown in the figure. Can you move... Read More

As shown in the figure, there are 4 numbers, 4, 5,... Read More

Puzzle Set 003 The Puzzle of the Chinese Emperor A chinese emperor had to choose a new adviser amongst 3 sages, all of them equally wise. He placed a problem to them: "To choose one of you,... Read More

Die: mean throws What is the expected number of times a fair die must be thrown until all scores appear at least once? Solution to puzzle : Die: mean throws What is the expected number of times a fair die must be thrown until all scores appear at... Read More

The Puzzle: The circumference of the Earth is approximately 40,000 kilometres, and someone has just made a metal band that circles the Earth, touching the ground at all locations. You come along at night, as a practical joke, and add just 10 metres... Read More

The Puzzle: You have six beads placed in a plane. The object is to find two pairs of equidistant beads. (In other words, find a pair of beads that are exactly the same distance apart as another pair of beads). The distance between two beads is... Read More

The Puzzle: An eccentric professor used a unique way to measure time for a test lasting 15 minutes. He used just two hourglasses. One measured 7 minutes and the other 11 minutes. During the whole time he turned the hourglasses only 3 times. How... Read More

The Puzzle: There’s a toy boat floating in a pool. Place a lead ball in the boat (without sinking it), and measure the level of water in the pool. Now take the ball out of the toy boat and drop it into the pool, and measure the water&rsquo... Read More

The Puzzle: You are on an island and there are three crates of fruit that have washed up in front of you. One crate contains only apples. One crate contains only oranges. The other crate contains both apples and oranges. Each crate is labeled. One... Read More

The Puzzle: Four people are traveling to different places on different types of transport. Their names are: Rachel, John, Mr.Jones and Cindy. They either went on train, car, plane or ship. * Mr.Jones hates flying * Cindy has to rent her vehicle *... Read More

The Puzzle: A man on a park bench is looking at a small portrait. You ask him, "Who is that in the picture?" The man says, "Brothers and sisters, I have none, but that man’s father, is my father’s son." Can you tell what person is in... Read More

The Puzzle: Place 10 balls in 5 lines in such a way that each line has exactly 4 balls on it. . . . . (Scroll down if you really want to see the Solution ...) . . . . . . The Solution . . . Read More

The Puzzle: Two ladies played cards for candy; the winner received one piece per game from the loser. When it was time for one of the ladies to go home, one lady had won three games, while the other lady had won three new pieces of candy. How many... Read More

The Puzzle: Big Jim, engineer of the Oval Express says: "We blew off a cylinder head an hour after leaving the station and had to continue the trip at three-fifths of the former speed, which brought us in two hours late. If the... Read More

The Puzzle: An Arab Sheik, finding himself about to die, called his sons about him and said: "Divide my camels among you in the proportion of one-half of the herd to the eldest son, the second son one-third, and to the youngest son one... Read More

The Problem: In your cellar there are three light switches in the OFF position. Each switch controls 1 of 3 light bulbs on floor above. You may move any... Read More

Math Riddles Math riddles are solved by pure logic. Unlike lateral thinking puzzles and other riddles, you usually don’t have to get creative to solve them. Still, there may be a surprising solution or two here. Give... Read More

Mind Numbing Puzzles Number Correct Mind Numbing Rank 0-1 Comfortably Numb 2-3 Sensationless 4-5 Some Feeling 6 Sensational 7-8 Resistant to Mind Numbing 9-10 ... Read More

We paint each face of the 4 feet cube with the color red, then cut the cube into 64 one foot... Read More

8 matches make a figure as shown. Can you add 2 more matches to make the area doubled. You... Read More

Long time ago, a rancher spent $100.00 and bought... Read More

Length of hypotenuse  Triangle ABC is right-angled at B.  D is a point on AB such that BCD = DCA.  E is a point on BC such that BAE = EAC.  If AE = 9 inches and CD = 8 inches, find AC. Solution to puzzle : Length of... Read More

Cuboids An a × b × c cuboid is constructed out of abc identical unit cubes -- a la Rubik’s Cube.  Divide the cubes into two mutually exclusive types.  External cubes are those that constitute the faces of the cuboid; internal cubes... Read More

The Puzzle: Eight folding patterns are scattered around a triangular prism as shown in the illustration. Determine all those patterns which form a prism, when folded along the lines. No parts should overlap each other. Author: Peter Grabarchuk ... Read More

The Puzzle: You are about to leave for holiday, but you forgot socks! You race back to your room, but all the lights are off, so you can’t see the color of the socks. Never mind, because you remember that in your drawer there are ten pairs of... Read More

The Puzzle: Five friends have their gardens next to one another, where they grow three kinds of crops: fruits (apple, pear, nut, cherry), vegetables (carrot, parsley, gourd, onion) and flowers (aster, rose, tulip, lily). 1. They grow 12 different... Read More

The Puzzle: Here is a pretty puzzle from Mother Goose’s story of Jack and Jill’s race for a pail of water. The distance to the top of the hill was 440 yards, which is just a quarter of a mile. Jack got... Read More

The Puzzle: An old man goes to a bank with a check of $200 and asks the cahier "Give me some one-dollar bills, ten times as many twos and the balance in fives!". What will the cashier do? . . . . ... Read More

The Puzzle: Charley Smalleash treats his best girl to a trolley ride, but on account of his limited resources they plan to walk back, so, if the car goes at the rate of nine miles an hour and they can walk at the rate of three miles an... Read More

  You have been promoted to pet detective while Ace Ventura guides some tourists on a safari. From the following clues, you must figure out who is the owner of each pet, and where the pet got lost. A rabbit and a dog are two of the... Read More

   Some definitions: Riddle - Anything that arouses curiosity or perplexes because it is unexplained, inexplicable, or secret. Puzzle - A game, toy, or problem, that requires ingenuity and often persistence in solving or assembling. ... Read More

Letters A to I is categorized into 4 groups. Assume the font we used here is Arial. ... Read More

Jimmie Dean has a 20m by 30m garden. Within the garden he opens up a 4m wide walkway. The... Read More

Fill in numbers 1, 2, 3, 4, 5, 6, 7, 8 and 9 into... Read More

Fill in numbers 1, 2, 3, 4, 5, 6, 7, 8 and 9 into boxes to make the equations work. ... Read More

Smart Cookie did you ever wonder how they make those pillsbury cookie dough rolls with the intricate faces inside them?  look Here and notice the intricate design they have somehow injected into their cookie... Read More

Puzzle Set 006 1. XYZ + AB = CDEF XYZ - AB = BGA All the letters have distinct values. find X, Y & Z 2. A man was on his way to a marriage in a car with a... Read More

Highest score  Suppose n fair 6-sided dice are rolled simultaneously.  What is the expected value of the score on the highest valued die? Solution to puzzle 50: Highest score Suppose n fair 6-sided dice are rolled simultaneously. ... Read More

The Puzzle: The founders of Hairytown decreed years ago that: 1. No two people can have the same number of hairs 2. No one can have 999 hairs. 3. No one can have more than, or the same number of hairs as, the population of the town The town has now... Read More

The Puzzle: In the middle of an otherwise empty field there lies a man wearing a pack. He is dead. There are no other clues visible. How did he die? . . . . (Scroll down if you really want to see the Solution ...) .... Read More

The Puzzle: A farmer wants to cross a river and take with him a wolf, a goat, and a cabbage. There is a boat that can fit himself plus either the wolf, the goat, or the cabbage. If the wolf and the goat are alone on one shore, the wolf will eat the... Read More

The Puzzle: Here is the original story of the Seignor and the monkey house as told by an eye witness. You see, the organ had seen its best days, and was sadly out of tune, but the Seignor’s staying powers were inexhaustible... Read More

The Government Subsidy Problem The government pays farmers a specific fee for each row of four trees that they plant. An enterprising, but dishonest farmer found a way of planting five rows of four trees using only ten trees. How did he do it... Read More

Take a rope to tie the handle of a cup as shown in the figure. Then tie the vertical end to... Read More

24 matches make a figure as shown. Can you remove 8 matches to make 5 squares with the same... Read More

48 matches made 16 small squares as shown in the figure. Can you move 4 matches to make 17... Read More

Can you use 9, 2, 2 and 2, to make a result number from 0 to 12. The restrictions are: ... Read More

The Oldest Plays the Piano Two MIT math grads bump into each other while shopping at Fry’s. They haven’t seen each other in over 20 years. First grad to the second... Read More

Making 24  Using only the numbers 1, 3, 4, and 6, together with the operations +, −, ×, and ÷, and unlimited use of brackets, make the number 24.  Each number must be used precisely once.  Each operation may be used zero or... Read More

Twelve marbles A boy has four red marbles and eight blue marbles.  He arranges his twelve marbles randomly, in a ring.  What is the probability that no two red marbles are adjacent? Solution to puzzle : Twelve marbles A boy has four red... Read More

The Puzzle: If I drive half-way to the city at 30 km/hour, how fast do I have to go for the rest of the way to make the average speed for the entire journey of 60 km/hour? . . . . (Scroll down if you really want to see the... Read More

The Puzzle: In front of you is a balance. Can you devise a system, using only 4 weights, that can measure any whole number of kilograms (1,2,3, etc) … a) ... up to 15 kg ? b) ... up to 40 kg ? c) ... up to 80 kg ? . . . . ... Read More

The Puzzle: You intend to fly non-stop around the world. But you can only go halfway around the world on a full tank. However you can arrange many planes exactly like yours to assist with refuelling. Assuming refuelling can be done midair,... Read More

The Puzzle: A man is stranded on an island covered in forest. One day, when the wind is blowing from the west, lightning strikes the west end of the island and sets fire to the forest. The fire is very violent, burning everything in its path, and... Read More

The Puzzle: Years ago, to puzzle his friends, a scientist gave one of four containers containing blue and/or yellow marbles to each of the friends; Tom, Dick, Harry, and Sally. There were 3 marbles in each container, and the number of blue marbles... Read More

The Puzzle: The five school children in couples weigh 129 pounds, 125 pounds, 124 pounds, 123 pounds, 122 pounds, 121 pounds, 120 pound, 118 pounds, 116 pounds and 114 pounds on a weighing machine. What was the weight of each one of... Read More

The Puzzle: A gypsy queen who ekes out a precarious existence by gathering quarters from gullible victims who want the future revealed, laments the decline of the fortune-telling industry as follows: "The week before last I... Read More

Hard Riddles Here are some hard riddles, and some not-so-hard riddles. The answers for almost all of them are at the bottom of the page. Almost, I say, because I am engaging in a bit of riddle-cruelty, and leaving you one to... Read More

Difficult Riddles Here are a few of the more difficult riddles in our collection. Afterwards, there is a list of other pages that have riddles, puzzles, and even some mind-stimulating jokes. 1. What English word is nine letters long, ... Read More

Funny Riddles Funny riddles are jokes really, but they still give you a chance to exercise your brain. A riddle after all, is just a form of lateral thinking puzzle. It leads you in one direction, but requires that you think in... Read More

The Ship in a Tub Problem - part 1 A toy ship is floating in a cylindrical container 10 centimeters in diameter that is partially filled with water. How much will the level of the water rise if a silver teddy bear weighing 100 grams is loaded... Read More

How many square inches are ins the shaded areas of the trapezoid? Puzzle... Read More

Can you cut the board into 6 pieces along with the dashed lines so each piece has the same... Read More

There are 5 balls in a 2 by 3 grid. You need to move 1 ball horizontally or vertically at a... Read More

16 matches made 8 small triangles as shown in the figure. Can you remove only 4 matches to... Read More

Wanna Play? i offer to play a card game with you using a normal deck of 52 cards.  the rules of the game are that we will turn over two cards at a time.  if the cards are both black, they go into my pile.  if... Read More

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Dice game Two students play a game based on the total roll of two standard dice.  Student A says that a 12 will be rolled first.  Student B says that two consecutive 7s will be rolled first.  The students keep rolling until one of them... Read More

Zero-sum game  Two players take turns choosing one number at a time (without replacement) from the set {−4, −3, −2, −1, 0, 1, 2, 3, 4}.  The first player to obtain three numbers (out of three, four, or five) which sum to 0... Read More

Five card trick, part 2 The two information theoreticians from puzzle 19 now attempt an even more ambitious trick.  It is in fact the same trick, but performed this time with a pack of 124 cards!  How does this trick work? (Note: 124 cards... Read More

Birthday line At a movie theater, the manager announces that a free ticket will be given to the first person in line whose birthday is the same as someone in line who has already bought a ticket.  You have the option of getting in line at any... Read More

Die: median throws What is the minimum number of times a fair die must be thrown for there to be at least an even chance that all scores appear at least once?  (Computer assistance advisable.) Solution to puzzle : Die: median throws What is the... Read More

Harmonic sum Let H0 = 0 and Hn = 1/1 + 1/2 + ... + 1/n. Show that, for n > 0, Hn = 1 + (H0 + H1 + ... + Hn−1)/n. (That is, show that Hn is one greater than the arithmetic mean of the n preceding values, H0 to Hn−1.) Solution to puzzle... Read More

Multiplicative sequence Let {an} be a strictly increasing sequence of positive integers such that: a2 = 2 amn = aman for m, n relatively prime (multiplicative property) Show that an = n, for every positive integer, n. Solution to puzzle :... Read More

Area of regular 2n-gon  Show that the area of a regular polygon with 2n sides and unit perimeter is , where there are n − 1 twos under both sets of nested radical signs. Solution to puzzle : Area of regular 2n-gon The regular octagon below... Read More

Greatest common divisor Let a, m, and n be positive integers, with a > 1, and m odd. What is the greatest common divisor of am − 1 and an + 1? Solution to puzzle : Greatest common divisor Let a, m, and n be positive integers, with a > 1,... Read More

We know very little about the life of the mathematician Diophantus (often known as the ’father of algebra’) except that he came from Alexandria and he lived around the year 250 AD. However, there remains a riddle that describes the... Read More

The Puzzle: Which area is bigger: the total orange or the total red? Author: Peter Grabarchuk This Puzzle © 2008 Peter Grabarchuk. All Rights Reserved. More from Peter Grabarchuk at PeterPuzzle.com . . . . (Scroll... Read More

The Puzzle: You are going to mix up some concrete, and in order to get it just right you need exactly 6 liters. But you only have a 4-liter and a 9-liter bucket. How can you do this? (You have an unlimited supply of water from the hose) ... Read More

The Puzzle: You have a balance and the following items of which you know the weights: a small coin weighing 5g, a pen weighing 10g, an eraser weighing 20g, a holepunch weighing 40g, and a stapler weighing 80g. How many different possible weights can... Read More

The Puzzle: In front of you is a balance. Can you devise a system, using only 4 weights, that can measure any whole number of kilograms (1,2,3, etc) … a) ... up to 15 kg ? b) ... up to 40 kg ? c) ... up to 80 kg ? . . . . ... Read More

The Puzzle: You have a balance scale with four weights. With these four weights you must balance any whole number load (in ounces) from 1 all the way up to 40. How much should each of the four weights weigh? (You may place weights on both sides of... Read More

The Puzzle: You have 10 bags full of coins, in each bag are 1,000 coins. But one bag is full of forgeries, and you can’t remember which one. But you do know that a genuine coins weigh 1 gram, but forgeries weigh 1.1 grams. To hide the... Read More

The Puzzle: You have three bags, each containing two marbles. Bag A contains two white marbles, Bag B contains two black marbles, and Bag C contains one white marble and one black marble. You pick a random bag and take out one marble. It is a... Read More

The Puzzle: There are five gears connected in a row, the first one is connected to the second one, the second one is connected to the third one, and so on. If the first gear is rotating clockwise what direction is the fifth gear turning? . ... Read More

The Puzzle: A Man works on the 10th floor and always takes the elevator down to ground level at the end of the day. Yet every morning he only takes the elevator to the 7th floor and walks up the stairs to the 10th floor, even when is in a hurry. ... Read More

The Puzzle: A boy and a girl are talking. "I am a boy" - said the child with black hair. "I am a girl" - said the child with white hair. At least one of them lied. Who is the boy and who is the girl? . . . . (Scroll down if... Read More

The Puzzle: There are three Athletes (Alex, Brook and Chris) and their individual Coaches (Murphy, Newlyn and Oakley) standing on the shore. No Coach trusts their Athlete to be near any other Coach unless they are also with them. There is a boat... Read More

The Puzzle: There is one four-digit whole number n, such that the last four digits of n2 are in fact the original number n. . . . . (Scroll down if you really want to see the Solution ...) . . . . . . ... Read More

The Puzzle: There are five people - Holly, Cameron, Julieanne, Alex and Jackie. Each one stole a special cookie of their favourite brand which was kept in a jar. Each person ate it in a particular place and drank their flavoured milk with it. *... Read More

The Puzzle: While enjoying a giddy ride at the carousel Sammy propounded a puzzle which reflects much credit to his mental abilities. "One third of the number of kids riding ahead of me, added to three-quarter of those riding... Read More

The Puzzle: What are the maximum number of grape vines that can be planted, not closer than nine feet apart, in a square plot containing one-sixteenth of an acre? (Note: each side of this square plot would be 52 feet 2 inches... Read More

The Puzzle: The hour and minute hands are at equal distance from the 6 hour, what time will it be exactly? . . . . (Scroll down if you really want to see the Solution ...) . . . . . . ... Read More

The Puzzle: In the Battle of Hastings that occurred on October 14, 1066 Harold’s forces formed 13 similar squares with exactly same number of soldiers in each square. When Harold himself joined the fray and was added to... Read More

The Puzzle: Solve the following: (DD)E= DEED . . . . (Scroll down if you really want to see the Solution ...) . . . . . . The Solution . . . 113 = 1331 Read More

The Puzzle: Solve the following: ABC × DEF = 123456, if A = 1 . . . . (Scroll down if you really want to see the Solution ...) . . . . . . The Solution . . . 192 × 643 = 123456 Read More

The Puzzle: Solve the following: ABCDEF × 3 = BCDEFA . . . . (Scroll down if you really want to see the Solution ...) . . . . . . The Solution . . . 285714 × 3=857142 or 142857 × 3=428571 Read More

The Puzzle: Solve the following: SEND + MORE = MONEY . . . . (Scroll down if you really want to see the Solution ...) . . . . . . The Solution . . . 9567 + 1085 = 10652 Read More

The Fruit Vendor Problem A fruit vendor bought 100 pounds of berries for $2.00 per pound and expected to double his investment by selling the berries for $4.00 per pound at an open-air market. The vendor only managed to sell 50 pounds of... Read More

A line is drawn from top left corner to bottom right of the outermost rectangle. Area A and... Read More

Using three 5s, you can make equations (as shown) to have target numbers such as 0 and 2.... Read More

Can you use 9, 7, 3, and 1, to make a result number from 1 to 13. The restrictions are: ... Read More

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Infinite product Find the value of the infinite product Solution to puzzle : Infinite product Find the value of the infinite product Factorizing numerator and denominator, we have k3 − 1 = (k − 1)(k2 + k + 1) k3 + 1 = (k + 1)(k2 − k +... Read More

Harmonic sum 2 Let Hn = 1/1 + 1/2 + ... + 1/n. Show that, for n > 1, Hn is not an integer. Solution to puzzle : Harmonic sum 2 Let Hn = 1/1 + 1/2 + ... + 1/n. Show that, for n > 1, Hn is not an integer. Consider, for n > 1, Hn = 1/1 +... Read More

Composite numbers  Take any positive composite integer, m. We have m = ab = cd, where ab and cd are distinct factorizations, and a, b, c, d 1. Show that an + bn + cn + dn is composite, for all integers n 0. Solution to puzzle : Composite... Read More

1000 divisors  Find the smallest natural number greater than 1 billion (109) that has exactly 1000 positive divisors.  (The term divisor includes 1 and the number itself.  So, for example, 9 has three positive divisors.) Solution to... Read More

How many outlines of triangles of all sizes and shapes can you trace in the figure? Author: Peter Grabarchuk This Puzzle © 2008 Peter Grabarchuk. All Rights Reserved. More from Peter Grabarchuk at PeterPuzzle.com Read More

The Puzzle: Four adventurers (Alex, Brook, Chris and Dusty) need to cross a river in a small canoe. The canoe can only carry 100kg. Alex weighs 90kg, Brook weighs 80kg, Chris weighs 60kg and Dusty weighs 40 kg, and they have 20kg of supplies. ... Read More

The Puzzle: This is a famous puzzle based on the show "Let’s make a deal". The host, Monty Hall, offers you a choice of three doors. Behind one is a sports car, but behind the other two are goats. After you have chosen one door, he reveals... Read More

The Puzzle: Here is a famous prize problem that Sam Loyd issued in 1882, offering $1000 as a prize for the best answer showing how to arrange the seven figures and the eight "dots" .4.5.6.7.8.9.0. which would add up to 82. ... Read More

The Puzzle: The clown after juggling with the five triangular pieces of cardboard to attract attention proceeds to cut one of them into two pieces. He then lays the six pieces upon the top of the box and shows that they will... Read More

The Bear Problem A bear walks south for one kilometer, then it walks west for one kilometer, then it walks north for one kilometer and ends up at the same point from which it started. What color was the bear? Answer: The bear was white... Read More

The Chicken and Leg Problem A chicken farmer also has some cows for a total of 30 animals, and the animals have 74 legs in all. How many chickens does the farmer have? Answer: This is a typical algebra problem with two unknowns, and we... Read More

Prediction: Your result will be 18 Think of a number. Add 7 to it. Subtract 2. Subtract your original number. Multiply by 4. Subtract 2. Explanation: This problem gives the... Read More

The grandson is about as many days old as the son is in weeks. The grandson is approximately as many months old as the father is in years. The ages of the grandson, the son, and the father add up to 120 years. What are their ages in years? ... Read More

The Aquarius Problem You have to measure exactly 4 liters of water, but you only have a 3-liter bottle and a 5-liter bottle. How do you do it? Answer: Fill the 3-liter bottle and pour it into the empty 5-liter bottle. Fill the 3-liter... Read More

There are 3 boxes labeled as box A, box B, and box C. Only one box has the gift you wanted,... Read More

The diameter of the big circle is 40 inches. What is the total circumferences of all 5... Read More

How many square cm are in the shaded area? Assume each side of the square is 10 cm. The... Read More

Move 4 matches to make 3 squares with different sizes. Puzzle Solution ... Read More

Move 2 matches to make 4 squares with equal sizes. Puzzle Solution ... Read More

17 matches to make a figure as shown. Can you remove 6 matches to make 2 squares? The... Read More

12 matches make a figure as shown. Can you move 4 matches to make 3 triangles. All triangles... Read More

24 matches made a figures as shown. Move 2 matches to make 4 polygons with the same shape ... Read More

Two pool balls  A cloth bag contains a pool ball, which is known to be a solid ball.  A second pool ball is chosen at random in such a way that it is equally likely to be a solid or a stripe ball.  The ball is added to the bag, the bag... Read More

Prime or composite?  Is the number 2438100000001 prime or composite?  No calculators or computers allowed! Solution to puzzle : Prime or composite? Is the number 2438100000001 prime or composite?  No calculators or computers allowed! ... Read More

Sum of two powers Show that n4 + 4n is composite for all integers n > 1. Solution to puzzle : Sum of two powers Show that n4 + 4n is composite for all integers n > 1. If n is even, then 2 divides n4 + 4n. Clearly (n4 + 4n)/2 > 2, for n ... Read More

The Puzzle: You are camping, and have an 8-liter bowl which is full of fresh water. You need to share this water fairly into exactly two portions (4 + 4 liters). But you only have two empty bowls: a 5-liter and a 3-liter bowl. Divide the 8 liters... Read More

The Puzzle: Seven matchsticks form two squares as shown in the illustration. Move three matchsticks to get three squares. You can rotate matchsticks, but you can’t overlap and/or damage them. Author: Peter Grabarchuk and Helen Homa This... Read More

The Puzzle: If you re-assemble the pieces of each of the four compositions shown below, three of them will be the same shape and one won’t. Which is the odd one out? Author: Peter Grabarchuk This Puzzle © 2007 Peter Grabarchuk. All... Read More

The Puzzle: Here is an odd little puzzle-game from the East: One of the Chinese girls writes sixteen letters on a slate in four rows, as shown, and after marking a straight dash, which connects A to B, passes the slate to her... Read More

The Puzzle: Here is an odd little puzzle which occurred the other day at an archery meeting. The young lady who carried off the first prize scored exactly one hundred points. Can you figure out how many arrows she must have... Read More

The Puzzle: A balloon propelled by some mechanical device travels five miles in ten minutes with the wind, but requires one hour to go back again to the starting point against the wind, how long would it have taken to go the whole... Read More

The Puzzle: Try to solve Sam Loyds Puzzle as shown here. Note: the illustration shows a top and three cubes equal in weight to 12 marbles, the second illustration shows a top is equal to a cube and eight marbles . . ... Read More

The Puzzle: How much does the baby weigh if the mother weighs 100 pounds more than the combined weight of the baby and the dog, and the dog weighs 60 percent less than the baby? . . . . (Scroll down if you... Read More

The Puzzle: The story of four elopements says that four men eloped with their sweethearts, but in carrying out their plan were compelled to cross a stream in a boat which would hold but two persons at a time. It appears that the young... Read More

The Problem Pool Balls You have 12 balls identical in size and appearance but 1 is an odd weight (could be either light or heavy). You have a set of scales (balance) which... Read More

A bank customer had £100 in his account. He then made 6 withdrawals, totaling £100. He kept a record of these withdrawals, and the balance remaining in the account, as follows:     ... Read More

The Jewelry Box   At an eBay auction, a woman’s ring and a filigree jewelry box with a hand-painted ceramic top are on sale for $200.00 Dollars. The jewelry box is valued at $190.00 Dollars more than the ring. How much is the ring... Read More

The Wall Street Investor $ $ $ An investor trading through a discount stock broker that charges $10.00 Dollars per transaction bought 200 shares of Vola Tile Corporation at $50.00 Dollars per share. The stock quickly increased in value by 50%,... Read More

The Odd Ball Problem There are twelve identical-looking balls, but one is either heavier or lighter than the other eleven. How can you determine which is the odd ball and find out whether this ball is heavier or lighter than the others using... Read More

Q: There are 3 gentlemen in a meeting: Mr. Yellow, Mr. Green and Mr. Brown. They are wearing yellow, green and brown ties. Mr. Yellow says: "Did you notice that the color of our ties are different from our names?" The person who is wearing the green... Read More

There was a burglary in the Silver City jewelry store again. A famous clock was stolen.... Read More

24 matches make a figure as shown. Can you remove 5 matches to make 6 squares with the same... Read More

12 matches make a figure as shown. Can you remove 3 matches to make 3 triangles with the... Read More

Using 14 matches to make an equation 1 + 2 + 3 = 4. However the equation is not correct. Can... Read More

16 matches make a figure as shown. can you move 5 matches to make the area reduced to the... Read More

12 matches make a figure as shown. Can you move 3 matches to reduce the area to 2/3 of the... Read More

You can not change the order of the digits. You... Read More

Triangular area In ABC, produce a line from B to AC, meeting at D, and from C to AB, meeting at E.  Let BD and CE meet at X. Let BXE have area a, BXC have area b, and CXD have area c.  Find the area of quadrilateral AEXD in terms of... Read More

Two logicians  Two perfect logicians, S and P, are told that integers x and y have been chosen such that 1 < x < y and x+y < 100.  S is given the value x+y and P is given the value xy.  They then... Read More

Equatorial belt  A snug-fitting belt is placed around the Earth’s equator.  Suppose you added an extra 1 meter of length to the belt, held it at a point, and lifted until all the slack was gone.  How high above the Earth’s... Read More

Reciprocals and cubes The sum of the reciprocals of two real numbers is −1, and the sum of their cubes is 4.  What are the numbers? Solution to puzzle 9: Reciprocals and cubes 1/x + 1/y = −1 (1) x3 + y3 = 4 (2) ... Read More

Making $1  You are given n > 0 of each of the standard denomination US coins: 1¢, 5¢, 10¢, 25¢, 50¢, $1.  What is the smallest n such that it is impossible to select n coins that make exactly a dollar? Solution to puzzle : Making $1... Read More

Isosceles angle Let ABC be an isosceles triangle (AB = AC) with BAC = 20°.  Point D is on side AC such that DBC = 60°.  Point E is on side AB such that ECB = 50°.  Find, with proof, the measure of EDB. Read More

Consecutive subsequence Given any sequence of n integers, show that there exists a consecutive subsequence the sum of whose elements is a multiple of n. For example, in sequence {1,5,1,2} a consecutive subsequence with this property is the last... Read More

Car journey  A car travels downhill at 72 mph (miles per hour), on the level at 63 mph, and uphill at only 56 mph  The car takes 4 hours to travel from town A to town B.  The return trip takes 4 hours and 40... Read More

The Puzzle: You need to boil eggs for exactly 9 minutes, or else the visiting Duchess will complain, and you will lose your job as head chef. But you have only 2 Hourglasses, one measures 7-minutes, and the other measures 4-minutes. How can you... Read More

The Puzzle: Two of the four jigsaw tiles have the same sum of their roots. Find these tiles. Author: Peter Grabarchuk This Puzzle © 2008 Peter Grabarchuk. All Rights Reserved. More from Peter Grabarchuk at PeterPuzzle.com . ... Read More

The Puzzle: Two trains are 200 km apart, and travelling towards each other at 50 km/hour each. From one train a fly takes off, flying straight above the rails to the other train at the speed of 75 km/hour, bounces off it and flies back to the first... Read More

The Puzzle: There are three different color cylindrical vessels: Blue, Red, and Green, with the sizes, as shown. The Red vessel is put into the Blue one, and the Green vessel into the Red one as shown. Each vessel is full of water. The object... Read More

The Puzzle: Real jelly babies have a mass of 10 grams, while imitation jelly babies have a mass of 9 grams. Spike has 7 cartons of jelly babies, 4 of which contain real jelly babies, the others imitation. Using a scale only once (and minimum... Read More

The Puzzle: Alex, Brook, Cody, Dusty, and Erin recently found out that all of their birthdays were on the same day, though they are different ages. On their mutual birthday, they were jabbering away, flapping their gums about their recent discovery... Read More

The Puzzle: Three sisters are identical triplets. The oldest by minutes is Sarah, and Sarah always tells anyone the truth. The next oldest is Sue, and Sue always will tell anyone a lie. Sally is the youngest of the three. She sometimes lies and... Read More

The Puzzle: In two decks of cards, what is the least amount of cards you must take to be *guaranteed* at least one four-of-a-kind? . . . . (Scroll down if you really want to see the Solution ...) . . . . . ... Read More

The Puzzle: It appears that an ingenious or eccentric teacher being desirous of bringing together a number of older pupils into a class he was forming, offered to give a prize each day to the side of boys or girls whose combined ages... Read More

The Puzzle: How it is that when I buy yellow bananas at three shillings a bunch and the same number of red ones at four shillings a bunch I would get two more bunches for the same amount if I divided the money evenly between the yellow... Read More

The Puzzle: Many years ago, when Barnum’s Circus was of a truth "the greatest show on earth" the famous showman got me [Sam Loyd] to prepare for him a series of prize puzzles ... Barnum was particularly pleased with the... Read More

The Puzzle: Solve the following: CAT = (C + A + T) × C × A × T . . . . (Scroll down if you really want to see the Solution ...) . . . . . . The Solution . . . 135 = (1 + 3 + 5) × 1 × 3 × 5 ... Read More

The Puzzle: 5 years ago Kate was 5 times as old as her Son. 5 years hence her age will be 8 less than three times the corresponding age of her Son. Find their ages. (Puzzle contributed by "Pratibha") . . . . (Scroll down... Read More

xx  If x is a positive rational number, show that xx is irrational unless x is an integer. Solution to puzzle 29: xx If x is a positive rational number, show that xx is irrational unless x is an integer. This question is amenable to a... Read More

Differentiation conundrum The derivative of x2, with respect to x, is 2x.  However, suppose we write x2 as the sum of x x’s, and then take the derivative: Let f(x) = x + x + ... + x  (x times) Then f’(x) = d/dx[x +... Read More

The Puzzle: In the illustration four flat cube-like shapes are shown. Their patterns are drawn with bold black lines. Which of them can you draw without taking your pencil off the paper or going along the same line twice? Which of them can’t be... Read More

Within the rectangle, draw a line to connect from circle 1 to the other circle 1, then draw... Read More

16 matches make a figure as shown. Can you move 3 matches to make 4 squares with the same... Read More

The Puzzle: There are five gears connected in a row, the first one is connected to the second one, the second one is connected to the third one, and so on. How much faster would the last gear be if the second gear was twice the size of the first... Read More

The Puzzle: Two school children, who were all tangled up in their reckoning of the days of the week, paused to straighten matters out over a circus poster, when little Priscilla, who was hinting for an invitation to the show, remarked to John; "When... Read More

The Puzzle: Solve the following: ABCD × D = DCBA . . . . (Scroll down if you really want to see the Solution ...) . . . . . . The Solution . . . 1089 × 9=9801 Read More

Assume the area of each small grid is one square inch, What is the total area of the polygon... Read More

There are 4 cardboards, two of them are 2 inches by 13 inches, and the other two are 3... Read More

14 matches made an area of 12 units. Can you move 8 matches to change the area to 8 units? ... Read More

22 matches made 7 squares as shown in the figure. Can you remove 7 matches to make 4... Read More

A spider has 8 legs. A dragonfly has 6 legs and 2 pairs of wings. A cicada has 6 legs and... Read More

The Puzzle: You have six squares (divided into 6x6 smaller squares). Each has a different pattern of holes. Which three of them can form an opaque (non-transparent) square when stacked on top of each other? Squares can be rotated and/or... Read More

The Puzzle: There are 7 boys on a soccer team. Each boy has a different position, jersey number, and height. Find out each person’s height, position, and number. * Justin is the goalie * The right forward is #10 * The goalie is 6’ 4... Read More

The Puzzle: A bicycle rider went a mile in three minutes with the wind, and returned in four minutes against the wind. How fast could he ride a mile if there was no wind? . . . . (Scroll down if you really... Read More

The area of EOF is a quarter of a circle with point O at the center of the circle. The line... Read More

8 matches made an unbrella as shown. Can you move 4 matches to make 2 unbrellas ... Read More

Yarr Maties Five pirates discover a chest full of 100 gold coins. The pirates are ranked by their years of service, Pirate 5 having five years of service, Pirate 4 four years,... Read More

Two ladders in an alley Two ladders are placed cross-wise in an alley to form a lopsided X-shape.  The walls of the alley are not quite vertical, but are parallel to each other.  The ground is flat and horizontal.  The bottom of each... Read More