You are a prisoner in a room with 2 doors and 2 guards. One of the doors will guide you to freedom and behind the other is a hangman --you don't know which is which...One of the guards always tells the truth and the other always lies. You don't know which one is the truth-teller or the liar either...You have to choose and open one of these doors, but you can only ask a single question to one of the guards.
What do you ask so you can pick the door to freedom?
This answer si actually a great one...one that is a hint to a larger clue of a puzzle I have been hinting forever at. Find out and I'll give you a next one.