Riddle about the Prisoner Princess

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PrisonPrincess, confined in dungeon, can break out if she solves the following riddle. She has two doors in front of her, one opens to freedom, the other is a way to death. She meets two guards at the doors. One of them can be either a “liar” (he will give you only misleading answers) or a “truth-sayer” (always tells the truth). The other guard is a “cunning fellow” who tells lies or truth by turns (he lies for odd-numbered questions and says the truth for even-numbered questions, or the other way around). Both guards know which door opens to freedom but our princess is not aware which guard is “cunning fellow”. The princess has the right to give two questions to one of the guards. How can she find her way out of prison? Note: give simple questions.

Please, if you want to solve the riddle yourself, be careful and do not read the comments on this brainteaser, there can be some who already wrote the solution there. We will publish the answer in the next brainteaser. You are always welcome to ask questions about the task, in case something is not clear. But sorry, don’t ask leading questions.

The answer to the previous riddle about Cinderella is: she threw all tomatoes into water; the ripe ones floated and unripe – sank. Some of you suggested it vice versa. Smiles4angels mixed up tomatoes and potatoes, but it was correct. Tobey, that’s right! We do believe you 🙂 And many thanks to Chris, who performed an experiment to find out the truth! By the way, we really liked another version you suggested: “She hands the bag to Prince Charming and tells him to sort the tomatoes into two piles – ripe and unripe within thirty seconds or he does not get any nookie for a week.”

Source of the image: flickr.com/photos/Moonfall.

11 COMMENTS

  1. This is an interesting puzzle since we are given more tools than are needed to find the solution. It can be solved by asking only one simple question. (Edward de Bono would be proud). The question to be posed is a hypothetical one, namely: “If I were to ask you if this door is the door that leads to freedom would you answer “Yes”? This only needs to be asked once of either guard standing in front of either door.
    The Logic:

    Assume for the first case that the door leads to freedom.
    If the guard is the truthful guard, or the cunning guard telling the truth, then he will answer “Yes”.
    If the guard is a liar (or the cunning guy lying) then he would have to answer “Yes” because he would be obliged to have to lie about the answer he would have ordinarily given (which would have been “No”) because the question is hypothetical. So we do not care if the guard is a truth teller, a liar or the cunning guy either telling the truth or lying (note that we have only asked one question) we get the information we need.

    The second case: If the door leads to death, given the exact same hypothetical question, (remember, we only ask the one question once of one of the guards) then the truthful guard will answer “No”.
    If the guard is a liar (or the cunning guy lying) he would have to lie about the answer he would have given (which would have been “Yes”). Hence he will have to answer “No”. Again we don’t care if the guard is truthful, a liar or the cunning guy either telling the truth or lying.

    So now we know which door leads to freedom.

    Note that the puzzle says that the Princess has the right to ask two questions, not that she is required to. If she is indeed required to ask two questions then she can ask some trivial and meaningless question such as “What is the meaning of life?” (You all know that the answer to that question is “42”).

  2. Apparently my previous post posed a question which was “not simple”.
    Therefore the question should be phrased and asked, to one of the guards, as follows:
    “Would you say this door leads to freedom?” Only eight words and very simple.
    No further questions are necessary since the previous logic applies. I challenge anyone to come up with two questions consisting of less than eight words which would solve the puzzle. Also, remember, that it is impossible to ask any question relating to what the other guard would say since it is not specified in the puzzle that either guard knows whether the other guard is a liar, truthful or the “cunning fellow” therefore we have no knowledge of this. The second question is, as before, redundant.

  3. Torture them until they both become truth-sayers. And then ask one single question – which door is to freedom?

  4. I guess she asked one of the guards the following:
    ‘are you a ‘cunning fellow’?’ and then ‘This door leads to freedom?’ – these are two simple questions.

  5. Ask each guard what the other guard would say…

    Liar guard will say that the truthful guard will say the door to death visa versa

    You take the opposite door

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