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.

Each made a statement:

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?

If C was a liar, that would mean B would have the key, thua meaning A and B would also be liars, so that is wrong. C has to be a knight.
C's and B's statements agree with each other, so B is also a knight. This means that, because there is at least one liar, A is a liar.
A says that he has the key, but he's a liar, so he definitely doesn'y have it.
B and C both say that B doesn't have the key, and they are knights, so B definitely doesn't have the key.
So by the process of elimination C must have the key.

Posted by Lewis on 2003-05-30 11:48:53