• # Brain Teasers & Puzzles

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• 100 prisoners are stuck in the prison in solitary cells. The warden of the prison got bored one day and offered them a challenge. He will put one prisoner per day, selected at random (a prisoner can be selected more than once), into a special room with a light bulb and a switch which controls the bulb. No other prisoners can see or control the light bulb. The prisoner in the special room can either turn on the bulb, turn off the bulb or do nothing. On any day, the prisoners can stop this process and say “Every prisoner has been in the special room at least once”. If that happens to be true, all the prisoners will be set free. If it is false, then all the prisoners will be executed. The prisoners are given some time to discuss and figure out a solution. How do they ensure they all go free?

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ravi Expert
• 1,430.0K views

• 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. No woman ever tells another woman if her husband is cheating on her.  So every woman in the town knows about all the cheating husbands in the town except her own. It can also be assumed that a husband remains silent about his infidelity. One day, the mayor of the town announces to the whole town that there is at least 1 cheating husband in the town. What do you think happens?

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ravi Expert
• 1,437.1K views

• # When can you add 2 to 11 to get 1 as the correct answer?Hint: many possible

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Anand Guru
• 1,431.2K views

• A bridge will collapse in 17 minutes.

4 people want to cross it before it will collapse. It is a dark night and there is only one torch between them.

Only two people can cross at a time.

“A” takes a minute to cross.
“B” takes 2 minutes.
“C” takes 5
and “D” takes 10 minutes

How do they all cross before the bridge collapses?

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Anand Guru
• 1,452.6K views

• 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 16 19

June 17 18

July 14 16

August 14 15 17

Cheryl then tells Albert and Bernard separately the month and the day of her birthday, respectively.

Albert: I don’t know when Cheryl’s birthday is, but I know that Bernard does not know, too.

Bernard: At first, I didn’t know when Cheryl’s birthday is, but I know now.

Albert: Then I also know when Cheryl’s birthday is.

When is Cheryl’s birthday?

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Anand Guru
• 1,429.8K views

• The owner of a banana plantation has a camel. He wants to transport his 3000 bananas to the market, which is located after the desert. The distance between his banana plantation and the market is about 1000 kilometer. So he decided to take his camel to carry the bananas. The camel can carry at the maximum of 1000 bananas at a time, and it eats one banana for every kilometer it travels.

What is the most bananas you can bring over to your destination?

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• 1,438.6K views

• You have 100 doors in a row that are all initially closed. you make 100 passes by the doors starting with the first door every time. the first time through you visit every door and toggle the door (if the door is closed, you open it, if its open, you close it). the second time you only visit every 2nd door (door #2, #4, #6). the third time, every 3rd door (door #3, #6, #9), ec, until you only visit the 100th door.

What state are the doors in after the last pass? Which are open which are closed?

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Anand Guru
• 1,439.1K views

• There is a building of 100 floors
-If an egg drops from the Nth floor or above it will break.
-If it’s dropped from any floor below, it will not break.
You’re given 2 eggs.
Find N

How many drops you need to make?
What strategy should you adopt to minimize the number egg drops it takes to find the solution?

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Anand Guru
• 1,598.2K views

• You are blindfolded and 10 coins are place in front of you on table.

You are allowed to touch the coins, but can’t tell which way up they are by feel. You are told that there are 5 coins head up, and 5 coins tails up but not which ones are which.

How do you make two piles of coins each with the same number of heads up?

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Anand Guru
• 1,441.8K views

• Prove that p^2 – 1 is divisible by 24 if p is a prime number greater than 3?

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Anand Guru
• 1,431.6K views

• ## More puzzles to try-

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• ### Man in telephone booth riddle

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• ### What Is The Price Of The Perfume?

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• ### Watch puzzle

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• ### Which glass fills first

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• ### How many people have guessed three fruits correctly, and how many people have guessed four fruits correctly?

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• ### Calculate the time

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• ### Help the Girl Puzzle

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• ### Two uneven ropes

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• ### How did the man died?

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• ### knot the string

How can you hold a piece of string, one end in each hand and tie a knot in the string ...Read More »
• ### The Swiss Cross

You can see a Swiss Cross in the attached picture. You can draw one on a sheet of paper. Now ...Read More »