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 Who has the key? (Posted on 2002-05-17)
An adventurer found a locked treasure chest in a dungeon. He tracked down three brothers (each either a Liar or a Knight) one of whom has the key to open the chest.

• A: I have the key to the chest.
• B: I don't have the key to the chest.
• C: B Doesn't have the key.

The adventurer knows that at least one of the three is a Liar, and at least one - a Knight. Who has the key?

•  See The Solution Submitted by levik Rating: 2.6000 (15 votes)

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 Puzzle Solution | Comment 14 of 16 |

If A had the key, then all the three adventurers spoke truthfully. This is a conttradiction since there must be at least one Liar.

If B had the key, then all the three adventurers spoke falsely. This is a conttradiction since there must be at least one Knight.

Hence C must have the key.
Consequently, C is the Knight as he spoke truthfully, B is the Knight as his statement is obviously true, and A is the Liar having lied about the identity of the owner of the key.

 Posted by K Sengupta on 2007-03-18 04:12:45

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