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(2): Solution - Not convinced
It so happens you use Penny's question, and Twin A answers: "If you
asked B this, he could answer 'Go and dig beneath that rock over
You happily go, excavate, and find nothing.
However, no rules were broken -- Twin A actually lied.
Can you find the error in the reasoning?
Posted by e.g.
on 2005-07-05 13:01:55