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| Barcelona-trekearth |
puzzlingstackexchange
Cited
'You are a prisoner in a room with 2 doors and 2 guards. One of the doors will guide you to freedom and behind the other is a hangman - you don't know which is which. One of the guards always tell the truth and the other always lies. You don't know which one is the truth-teller or the liar either. You have to choose and open one of these doors, but you can only ask a single question from one of the guards. What do you ask to lead you to the door of freedom?'
'The answer I've consistently heard to this is: If I asked what door lead to freedom, what door would the other guard point to? If you asked the truth-guard, the truth-guard would tell you that the liar-guard would point to the door that leads to death. If you asked the liar-guard, the liar-guard would tell you that the truth-guard would point to the door that leads to death. Therefore, no matter who you ask, the guards tell you which door leads to death, and therefore you can pick the other door.'
Further
'This assumes that the liar guard will only tell a lie. (As opposed to trying to deceive you.) There is more to lying than words - there is body language.'
End
In my short audio/video presentation I explain that in Bible School I came up with a similar idea independently.
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| Hallstatt, Austria-Facebook |
