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?
Well they are both Liars... Call them Thing A and Thing B (Cat in the
hat anyone?)... Thing A says one of them is a knight, and Thing B says
one is a liar...
Assume A is a knight, well B can't be a liar because B said one is a
liar and if A is a knight, then B should be the liar, but he didnt
lie...
Assume B is the knight... then A would have to be a liar but by saying
one of them is a knight he is telling the truth, so this cant be
right...
Now assume A is a Liar, in which case they are both Liars and when B says one is a Liar he is also lying so that is okay...
So they are both liars... now the question is, where is the treasure?
You know that regardless of which you ask, they will tell you the
opposite, so if you ask them to lead you away from the treasure they
will lead you towards it... right?

Posted by sean
on 20050830 03:33:48 