All Puzzles

  • This old one runs forever but never moves at all. He has not lungs nor throat, but still has a mighty roaring call who is he?

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    • 111 views
    • 2 answers
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  • A pirate ship captures a treasure of 1000 golden coins. The treasure has to be split among the five pirates: 1, 2, 3, 4, and 5 in order of rank. The pirates have the following important characteristics:

    Infinitely smart.
    Bloodthirsty.
    Greedy.

    Starting with pirate 5, they can make a proposal how to split up the treasure. This proposal can either be accepted or the pirate is thrown overboard. A proposal is accepted if and only if a majority of the pirates agrees on it.

    What proposal should pirate 5 make?

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    • 153 views
    • 3 answers
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  • There’s a man lying dead in a telephone booth beside a river. The phone is off the hook, and there is smashed glass on the floor of the phone booth. What happened?

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    • 144 views
    • 1 answers
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  • how many places are there on the earth that one could walk one mile south, then one mile west, then one mile north and end up in the same spot? to be precise, let’s assume the earth is a solid smooth sphere, so oceans and mountains and other such things do not exist. you can start at any point on the sphere. also, the rotation of the earth has nothing to do with the solution; you can assume you’re walking on a static sphere if that makes the problem less complicated to you.

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    • 150 views
    • 1 answers
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  • Army General, accused of high disloyalty, is sentenced to death by the court-martial. He is allowed to make a final statement, after which he will be shot if the statement is false or will be hung if the statement is true. General makes his final statement and is released.

    What could he have said?

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    • 169 views
    • 2 answers
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  • Four white pieces (the mice) are placed on one side of a chessboard, and one black piece (the cat) is placed at the opposite side. The game is played by the following rules:

    black wins if it reaches the opposite side;
    white wins if it blocks black in such a way that black cannot make any move anymore;
    only diagonal moves (of length 1) on empty squares are allowed;
    white only moves forward;
    black can move backward and forward;
    black may make the first move, then white makes a move, and so on.

    Is this game computable (i.e. is it possible to decide beforehand who wins the game, no matter how hard his opponent tries to avoid this)?

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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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    • 194 views
    • 1 answers
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  • Jacob and John are competing for the same girl. After years of battling, both decide to settle it by tossing a coin.

    John produces a coin, but Jacob doesn’t happen to have one on him. Jacob is sure that the coin John has produced is loaded, i.e. it will come up with heads more than 50% of the time on average.

    How do Jacob arrange a fair contest, based purely on chance and not skill, by flipping this coin?

    Variation: (COIN BIASING) Jacob and John are competing for the same girl, and decide to settle it with a coin toss. John has known the girl longer than Jacob have, so Jacob agree that it is fair for him to have a chance of winning equal to P, where P > 0.5. However, Jacob only have a fair coin. How can you conduct this contest such that the biased probability is manifested? What is the average number of coin flips needed to determine a winner?

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    • 285 views
    • 1 answers
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  • A prisoner fate will be determined by a game. there are two jars, one with 100 white marbles, and one with 100 black marbles. at this point, prisoner is allowed to redistribute the marbles however he wish e.g. swap a black marble with a white marble, etc. the only requirement is that after prisoner is done with the redistribution, every marble must be in one of the two jars. Afterwards, both jars will be shaken up, and prisoner will be blindfolded and presented with one of the jars at random. then he pick one marble out of the jar given to him. if the marble prisoner pull out is white, prisoner live; if black, prisoner die. how should prisoner redistribute the marbles to maximise the probability that he live; what is this maximum probability (roughly)?

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    • 300 views
    • 1 answers
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  • You want to send a valuable object to a friend.

    You have a box which is more than large enough to contain the object.

    You each have several locks with keys, but not keys to each other’s locks.

    The box has a locking ring which is large enough to have many locks attached.

    You cannot send a key in an unlocked box, since it might be copied.

    How do you do it?

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    • 362 views
    • 1 answers
    • 0 votes