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Posers and Puzzles

Posers and Puzzles

  1. 29 Apr '03 21:28 / 1 edit
    Here's a puzzle that I recall from my childhood (so it's old).

    You're in a room with two exits (and no idea how you got there). The exits appear to be exactly the same except one exit leads to safety and the other to certain death. Beside the doors stand identical twins. One always lies and the other always tells the truth. You are allowed one question to one of the twins to help you decide which exit to take. What do you ask?

    Note that this puzzle assumes no suicidal tendencies (i.e. you're looking for the safe exit)
  2. Standard member royalchicken
    CHAOS GHOST!!!
    29 Apr '03 22:13
    "What would the other twin say is the door to safety?" Then take the other door. The truthful twin would point to the death door, because the other twin would lie. The lying twin would point to the death door because he is lying about what the truthful one would say.
  3. 29 Apr '03 22:19
    You've heard it before?
  4. Standard member royalchicken
    CHAOS GHOST!!!
    29 Apr '03 22:21
    No; very good puzzle. You should post here more. However, I've heard a similar one:

    There are two cities at a fork in the road, the City of Truth and the City of Lies (whose denizens are truthful and lying respectively). You meet someone on the way to the cities, and you want to ge to the city of truth. Assuming this person is from one of those cities, what do you ask?
  5. 29 Apr '03 22:23
    Ahhh yes - it's pretty much the same puzzle.
  6. Standard member royalchicken
    CHAOS GHOST!!!
    29 Apr '03 22:24 / 1 edit
    Only cosmetically is it the same. What is the answer? The question you must ask is of a slightly different nature.
  7. Donation bbarr
    Chief Justice
    29 Apr '03 22:49
    Originally posted by royalchicken
    Only cosmetically is it the same. What is the answer? The question you must ask is of a slightly different nature.
    Ask him: "Which fork should I take to get to your home town?"
  8. Standard member royalchicken
    CHAOS GHOST!!!
    29 Apr '03 22:52
    Very good !
  9. 15 May '03 20:49 / 1 edit
    Here's a variant that may be less familiar.
    As a supposedly skilled logician approaching the Pearly Gates, you are escorted into an ante-room by three spirits. You know that one of them is Gandhi, who never lies, another is Goebbels, who always lies and the third is De Gaulle, who may or may not lie, but (amazingly or not) you can't tell which is which.
    There are two doors out of the room, one leads to Heaven and the other to Hell and you may ask two questions, which may (if you wish)be addressed to separate spirits. Assuming you prefer Heaven, how should you proceed?
  10. Standard member royalchicken
    CHAOS GHOST!!!
    16 May '03 22:23
    The key is to rule out De Gaulle, and reduce it to the previously solved problem. First, creatively denote the three spirits A, B, and C. Then say to A "Is it more likely that B tells me the truth than C does?" If A responds affirmatively:

    A says "yes":

    C is not De Gaulle

    If A says "no":

    B is not De Gaulle

    Either way, we have isolated one person whose truth-telling habits are known. So if A says 'yes', then ask C the same question you would if there were two people. If A says 'no', then ask the same question of B.
  11. 31 May '03 04:48 / 1 edit
    (I'm new to the forums)
    When I came, I expected to see chess puzzles...
    But anywho...ahh, riddles - I am the master of riddles.
    The following (although not quoted word for word) is from possibly the most famous logical thinker of recent times, Raymond Smullyan. I believe I read it in his book, "Alice in Puzzleland" (although it might have been "What is the Name of this Book?&quot. It resembles the others, but it's much harder (and if you've heard it before, please don't say the answer). Oh, and PLEASE read over the riddle before you answer; you wouldn't believe how many times I've posted this in a forum, only to have someone who thought they've heard it before answer it with a completely unfitting (and ignorant) response:
    You are at a fork in the path in the jungle. For some reason or another you cannot venture from the path, nor can you turn around and go back from whence you came. One path holds certain doom, the other certain safety, although you don't know which is which. Both paths harbor a tribe (that is, somewhere in the distance, along each path, are tribes of natives). Either tribe could be truth tellers or liars (which means BOTH tribes could be liars or BOTH truth tellers, or one of each). Standing at the fork are two natives. You don't know whether each is a truth-teller or a liar, nor do you know what tribe they came from (that is, both could be from the same tribe, or they could come from seperate tribes; both could be truth-tellers, both liars, or again, one of each).
    You get to ask both natives one question each. You must be absolutely certain that, with the given information and the questions you ask, you'll be taking the path of safety. What do you ask?
  12. Donation bbarr
    Chief Justice
    01 Jun '03 00:54
    Originally posted by Fisching
    (I'm new to the forums)
    When I came, I expected to see chess puzzles...
    But anywho...ahh, riddles - I am the master of riddles.
    The following (although not quoted word for word) is from possibly the most famous logical thinker of recent times, Raymond Smullyan. I believe I read it in his book, "Alice in Puzzleland" (although it might have been "What ...[text shortened]... n information and the questions you ask, you'll be taking the path of safety. What do you ask?
    I think most of the details in this puzzle serve only as distraction. I don't think it makes a difference whether there are two natives, two tribes, etc. All that really matters is that there is at least one native who is either a compulsive liar or a compulsive truth-teller. You should ask the first native "Would you answer 'yes' if I asked you whether the path you stand before leads to safety?". If he is a truth-teller, and the path he stands before leads to safety, he will answer 'yes'. If he is a liar, and the path he stands before leads to safety, then he would also answer 'yes' to the question above. So in either case, if you receive 'yes' as the answer, take the path behind the first native, and if you receive 'no' as the answer take the path behind the second native.
  13. 02 Jun '03 12:35
    Good job
    The actual answer in the book was "What would you say if I asked you '_____'": it can be used to solve just about any of these types of problems...