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(4): Solution - WRONG ANSWER, NEW PUZZLE
Actually asking one twin what the other one will say doesn't work, because Twin A could always say that Twin B's response is going to be "I'm a Liar, so why are you asking me ?", or "It may or may not be at location x."
Fletch has the right answer: ask either twin to give you a location that does NOT contain the treasure.
Edited on July 5, 2005, 3:20 pm
Posted by Penny
on 2005-07-05 15:18:02