Professor Z was killed by one of his four students, who was helped by another of the four. His students declared:

A: If B is guilty of something, then C must be innocent.
B: If A is innocent, then C must be guilty.
C: If B was the killer, then D must have had nothing to do with the crime.
D: I am innocent.

As everybody should know, guilty parties always lie, and innocent people always tell the truth. Who killed the professor, and who was his accomplice?

(In reply to Help me out... by Jeremy Trenary)

JT: "I don't understand how it can be assumed that if a person is lying, that the opposite of his statement is true."

That is not so. If I lie and say "Toronto is due west of where I live", that does not mean that Toronto is east of me (east = opposite of west). It only means that Toronto is not west of me. My statement must be false; otherwise I wouldn't be lying. "If X, then Y" is false only if X is true and Y is false. But is a true statement otherwise. For instance, "If Toronto is a city in China, then eating hamburgers will increase your IQ by 50 ponts" is a TRUE statement. A false statement is ""If Toronto is a city in Canada, then eating hamburgers will increase your IQ by 50 ponts". Don't blame me for these strange rules. They were invented by Greek shipping tycoon Aristotle Onassis, Jackie Kennedy's second husband. (I read that somewhere...)  

Posted by Penny on 2004-06-25 16:05:08