Here's an old one... You are out walking to go to a certain village -and come to a fork in the road. Just before you come to the fork, you meet two brothers who live locally and know where the village is. One always tells the truth and the other always tells lies- but you don't know which is which.
You are allowed to ask one question only- to ensure that you take the correct fork to your destination.
What is the question you must ask?
"Which way would your brother tell me to go"? Then you go the other way


