Alan, Barry and Carl (each either a Knight or a Liar) were rounded up by the cops yesterday, because one of them was suspected of having stolen money from the bank. The three brothers made the following statements under very intensive questioning:
Alan: I'm innocent.
Barry: I'm innocent.
Carl: Barry is the guilty one.
If only one of these men is a Knight, who stole the money?
(In reply to
answer by K Sengupta)
Assume that Alan is the knight. Then both Barry and Carl are liars. Then, Barry's false statement marks him as guilty but, according to Carl's false statement Barry is innocent. This is a contradiction.
Assume that Carl is the knight. Then, both Alan and Barry are liars. By Carl's true statement, Barry is guilty. But Alan's false statement also marks him as the guily person. Thus, both Alan and Barry are guilty. Contradiction.
Assume that Barry is the knight and, Alan and Carl are liars.By Barry's true statement, it follows that he must be innocent.This is corroborated by Carl's false statement. Alan is falsely saying that he is innocent, and accordingly he must be the guilty person. Therefore, this case is fully in consonance with the given conditions.
Summarizing, we have:
Alan is a liar, and he stole the money.
Barry is the knight.
Carl is a liar.
Explanation for Puzzle Answer
