You meet three people, A, B, and C. Each one is either a knight or a liar. A and B make these statements.

A:We are all of the same type.
B:A and C are of different types.

What are A, B, and C?

A = Liar
B = Knight
C = Knight

If [A = Knight], then [B & C = Knight].  But that would make B's statement False.  Therefore, [A = Liar].

If [B = Liar], then A & C would be the same - Liars.  But that would make all three Liars, thus making A's statement True.  Therefore, [B = Knight].

And if [B = Knight], then C must be the opposite of A, so [C = Knight] too.

Posted by hoodat on 2011-02-14 13:12:12