Puzzles

Commonly asked Interview Puzzles

  • Palindrome Date

    On October 2, 2001, the date in MMDDYYYY format was a palindrome (same forwards as backwards). 10/02/2001, When was this occured before October 2,2001?

  • Four People and Bridge

    The puzzle is Four people need to cross a rickety bridge at night. Unfortunately, they have only one torch and the bridge is too dangerous to cross without one...

  • King Octopus and Servants

    King Octopus has servants with six, seven, or eight legs. The servants with seven legs always lie, but the servants with either six or eight legs always say the truth...

  • 100 swords

    100 people standing in a circle in an order 1 to 100. Person at No.1 has a sword. He kills next person (i.e. no. 2) and gives sword to next to next (i.e no.3). All person does the same until...

  • Probability of Boat

    A man watches the boats from a light house. He finds that the probability of a boat passing the lighthouse in a 20 minute window is 0.9. Then what is the probability of a boat passing the light house in a 5 minute window?

  • Measure 6 liters

    You have a jar containing 12 litres of water and two more jars of capacity 5 and 7 litres each, you have to measure 6 litres of water without wasting any quantity of water.

  • 100 Meter Race

    Rooney, Hernandez, and Robin race each other in a 100 meters race. All of them run at a constant speed throughout the race. Rooney beats Hernandez by 20 meters. Hernandez beats Robin by 20 meters. How many meters does Rooney beat Robin by ?

  • 9 dots puzzle

    Nine dots arranged in a square matrix, each of them being equidistant from its neighbors. Join all the dots up with not more than 4 continuous straight lines.

  • Riding Against the Wind

    A horse rider went a mile in 5 minutes with the wind and returned in 7 minutes against the wind. How fast could he ride a mile if there was no wind?

  • Strategy for Rabbit

    Consider five holes in a line. One of them is occupied by a rabbit. Each night, the rabbit moves to a neighboring hole, either to the left or to the right. Each morning, you get to inspect a hole of your choice. What strategy would ensure that the rabbit is eventually caught?

  • Batteries Problem

    A man buys three kinds of batteries for his expedition adventure from a supply store. One of the batteries cost Rs. 5 each; the other costs cost Rs. 3 each and the third one costs just Rs. 0.5 each piece. He buys a total of 100 batteries costing him Rs 100. How many of each do you think he buy?

  • Find the Ages

    Priyanka and Rubina are having a conversation.Priyanka: I am definitely not over 30.Rubina: I am 28 and you are surely 5 years older to me at least.Priyanka: No, you are at least 29.

  • Sand Timer Puzzle

    You have two sand timers with you. One can measure 7 minutes and the other sand timer can measure 11 minutes. This means that it takes 7 minutes for the sand timer to completely empty the sand from one portion to the other...

  • Hats and Students

    Nine IIT students were sitting in a classroom. Their professor wanted them to test. Next day the professor told all of his 9 students that he has 9 hats, The hats either red or black color. He also added that he has at least one hat with red color and the no....

  • Twelve Coins

    You have 12 coins all look identical (in shape, color etc.). All of them have same weight except one defective coin. You don’t know that the defective one is heavier or lighter than other coins. You can use a two sided balance system (not the electronic one What is the minimum number of times you will need to use the balance (and how would you do it) to determine...

  • Six colored balls

    We have two red, two green and two yellow balls. For each color, one ball is heavy and the other is light. All heavy balls weigh the same. All light balls weigh the same. Find the minimum number of weighings needed to identify the three heavy balls?

  • Flower Pot

    Sara has 6 flower pots, each having a unique flower. Pots are arranged in an arbitrary sequence in a row. Sara rearranges the sequence each day but not two pots should be arranged adjacent to each other which were already adjacent to each other in previous arrangement. How many days she can do this or how many such arrangements are possible ?

  • Poisoned Wine Barrels

    An enemy spy has poisoned one out of 1000 barrels of wine in a king's cellar. Even a sip of the poisoned wine has potency to kill. However, the effects of the poison show only in 30 days...

  • Rope Escape

    Rajeev is trapped atop a building 200m high. He has with him a rope 150m long. There is a hook at the top where he stands. Looking down, he notices that midway between him and the ground, at a height of 100m, there is a ledge with another hook. In his pocket lies a Swiss knife....

  • A Gold for 7 days of Work

    You’ve got someone working for you for seven days and a gold bar to pay them. You must pay the worker for their work at the end of every day. If you are only allowed to make two breaks in the gold bar, how do you pay your worker?

  • A Box of Defective Balls

    You have 10 boxes of balls (each ball weighing exactly10 gm) with one box with defective balls (each one of the defective balls weigh 9 gm). You are given an electronic weighing machine and only one chance at it. How will find out which box has the defective balls?

  • Is Your Husband a Cheat ?

    A certain town comprises of 100 married couples. Everyone in the town lives by the following rule: If a husband cheats on his wife, the husband is executed as soon as his wife finds out about him. All the women in the town only gossip about the husbands of other women...

  • Burn the Ropes

    You find yourself locked in a room which is filled with nothing but ropes of various length and composition. All of these ropes have inconsistent compositions and densities, even within themselves, but they all have one common property:

  • Cut the Rectangle

    How do you cut a rectangular cake into two equal pieces? When someone has already removed a rectangular piece from it.

  • 100 Locks Puzzle

    Over at your local high school, the main hallway has a bank of 100 lockers. All of these lockers, labeled 1 through 100, start with their doors closed.

  • Measure 4 Liters

    You have a 3-litre bucket, a 5-litre bucket, and an infinite supply of water. How can you measure out exactly 4 litres?

  • Red and Blue Marble

    You have two jars, 50 red marbles and 50 blue marbles. You need to place all the marbles into the jars such that when you blindly pick one marble out of one jar, you maximize the chances that it will be red. When picking, you’ll first randomly...

  • River, Soldier and Boat

    Consider there are 10 soldiers on the one side of the river. They need to go to the over side of the rever. There is no bridge in the rever and no one can swin in the rever. One of the soldiers spots the boat with two boys inside. The boat is very small and the boys in the boats also very small...

  • Find the contaminated Pill

    You have five jars of pills. All the pills in one jar only are contaminated. The only way to tell which pills are contaminated is by weight...

  • Three Ants

    Three ants are sitting at the three corners of an equilateral triangle. Each ant starts randomly picks a direction and starts to move along the edge of the triangle. What is the probability that the ants collide?

  • Supersonic Bee

    Two trains enter a tunnel 200 miles long, traveling at 100 mph at the same time from opposite directions. As soon as they enter the tunnel a supersonic bee flying at 1000 mph starts from one train and heads toward the other one...

  • Two Numbers

    There is a one person who have two numbers, he tells sum to the person S and product of those numbers to P. Now there is this conversion between S and P...

  • 5 Pirates and 100 Gold Coins

    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 (including the oldest) vote for or against it.

  • Gate to Heaven

    Amanda dies and reaches at the gate of heaven. She has three doors in front of her out of which only one of them leads to heaven. Out of the other two gates, one leads to hell for one day and then back to the gate and one leads to hell for two days and then back to the gate. If she chooses one of these two gates, the gates are shuffled when she returns back....

  • Cost of Pizza

    Jasmine, Thibault, and Noah were having a night out and decided to order a pizza for $10. It turned out that Jasmine and Thibault were hungrier than Noah. They both ate 6 slices a piece, and Noah got to eat just 2 slices...

  • Cheryl's Birthday

    Puzzle: Albert and Bernard just became friends with Cheryl, and they want to know when her birthday is. Cheryl gives them a list of 10 possible dates. May 15 May 16 May 19 June 17 June 18 July 14 July 16 ...

  • Balls in A Bag

    You have 20 blue balls and 14 red balls in a bag. You put your hand in and remove 2 at a time. If they’re of the same color, you add a blue ball to the bag. If they’re of different colors, you add a red ball to the bag. (assume you have a big supply of blue & red balls for this purpose...

  • Average Salary

    Four honest and hard-working computer engineers are sipping coffee at Starbucks. They wish to compute their average salary. However, nobody is willing to reveal an single bit of information about his/her own salary to anybody else. How do they do it?


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