You are on a treasure hunt, wondering where the "Truth Treasure" is buried. You have no idea where it is buried, so you go Truth Town (made up of only Liars and Knights) because it is famous for holding the treasure's secret location.
When you enter the city, you see two twins and they know each other's types, but you don't. One twin says "(Exactly) one of us is a Knight..." and the other twin says "...and (exactly) one of us is a Liar." You can only ask one question and only to one person. You only care about where the treasure is kept, and obviously a liar would give you a wrong answer, so what should you do?
(In reply to
re(3): Solution  WRONG ANSWER, NEW PUZZLE by e.g.)
If Twin A answers: "If you asked B this, he could answer 'Go and dig beneath that rock over there'", and the treasure isn't there, then Twin A is telling the truth, because "Go and dig beneath that rock over there", if said in answer to the question "Tell me where the treasure is", is by implication an answer to the question, and a lie if the treasure isn't there. A lie is no less a lie if disguised by equivocation. In a court of law, it would be considered a lie and an act of perjury if the treasure were not actually there. So then Twin A would be telling the truth.
Edited on October 20, 2007, 6:43 pm

Posted by Penny
on 20050705 14:50:15 