Meet Andy, Bob and Chris. We know one of them always tells the truth, one always lies and another does a bit of both. Andy says, “Chris is the one who mixes truth and lies.” Bernie says, “Andy is a liar.” And Chris says, “I mix truth and lies.” Which is which?
Reveal the solution
Chris can’t be the consistent truth teller, because his statement would be a lie. Now if we imagine Bernie was the truth teller then his statement would mean Andy is the compulsive liar, but he can’t be because Andy’s statement about Chris would be true. So that only leave the option of Andy being the truth-teller, making Chris the one who mixes truth and lies, and Bob the liar.
Adapted from a puzzle by Raymond Smullyan.