• Brain Teasers & Puzzles

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    • You have two jugs. One jug has a content of 3 litres and the other one has a content of 5 litres.

      How can you get just 4 litres of water using only these two jugs?

      (There is plenty of water available to refill the jugs)

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    • A light bulb is hanging in a room. Outside of the room, there are three switches, of which only one is connected to the lamp. In the starting situation, all switches are ‘off’ and the bulb is not lit.

      If it is allowed to check in the room only once to see if the bulb is lit or not (this is not visible from the outside), how can you determine with which of the three switches the light bulb can be switched on?

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    • A confused bank teller transposed the dollars and cents when he cashed a cheque for Ms Denial, giving her dollars instead of cents and cents instead of dollars. After buying a newspaper for 50 cents, Ms Denial noticed that she had left exactly three times as much as the original cheque. What was the amount of the cheque ?

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    • Jacob has three boxes with fruits in his barn: one box with apples, one box with pears, and one box with both apples and pears. The boxes have labels that describe the contents, but none of these labels is on the right box.

      How can Jacob determine what each of the boxes contains, by taking only one piece of fruit from one box?

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    • Assume that you have a number of long fuses, of which you only know that they burn for exactly one hour after you lighted them at one end. However, you do not know whether they burn with constant speed, so the first half of the fuse can be burnt in only ten minutes while the rest takes the other fifty minutes to burn completely. Also, assume that you have a lighter.

      How can you measure exactly three quarters of an hour with these fuses?

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    • On the game of Poker, two people play as follows:
      Player 1 takes any 5 cards of his choice from the deck of 52 cards. Then player 2 does the same out of the remaining 47. Then player 1 may choose to discard any of his cards and replace them from the remaining 42. Then player 2 may discard any of his cards and replace them, but he may not take player 1’s discards. ALL of the transactions with the deck are public knowledge, unlike the real game of Poker.

      After this process, the winner is the one who has the better poker hand. For the benefit of those who have not played poker, these are the highest ranking hands, in decreasing order of value:

      Royal Flush: the A K Q J 10 of the same suit.
      Straight Flush: any five consecutive of one suit. Highest card of the five is the tiebreaker. No one suit is more powerful than another.
      Four of a kind: all four of one rank (i.e. four aces). A hand with 4 aces outranks 4 kings, etc.
      Full house: a pair of one rank and 3-of-a-kind in another rank, i.e. Q Q 8 8 8.
      Flush: Any 5 cards of the same suit that don’t satisfy #2.
      Because of the clear advantage of player 1, the win is given to player 2 if the hands are equal in strength.

      Which player would you rather be? What strategy do you use?

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    • On the right, you see a paper with a chessboard print on it. We want to cut the chessboard paper into pieces (over the lines!) such that each piece has twice as much squares of one color than of the other color (i.e. twice as much black squares as white squares or twice as much white squares as black squares).

      Is it possible to do this? Give a proof!

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    • You are given “n” coins of denominations 1, 0.5, 0.25, 0.1, 0.05 and 0.01 (6n coins altogether). You are then asked to choose n out of these 6n coins that sum up to exactly 1. What is the smallest n for which this is impossible?

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    • Jenny has boxes in three sizes: large, standard, and small. She puts 11 large boxes on a table. She leaves some of these boxes empty, and in all the other boxes, she puts 8 standard boxes. She leaves some of these standard boxes empty, and in all the other standard boxes, she puts 8 (empty) small boxes. Now, 102 of all the boxes on the table are empty.

      The question: How many boxes has Jenny used in total?

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    • A stopped clock gives the exact time twice a day, while a normally running (but out of sync) clock will not be right more than once over a period of months. A clever grandfather [as in grandfather clock] adjusted his clock to give the correct time at least twice a day, while running at the normal rate. Assuming he was not able to set it perfectly, how did he do it?

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