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**smkxn** There is this exercise in the "Discreet Mathematics" book I'm reading for my computer science course, which is leaving me scratching my head.

This one question goes like this: "Each inhabitant of a remote village always tells the truth or always lies. A villager will only give a Yes or a No response to a question a tourist asks. Suppose you are a tourist visiting this area and come to a fork in the road. One branch leads to the ruins you want to visit, the other branch leads deeper into the jungle. A villager is standing at the fork in the road. What one question can you ask the villager to determine which branch to take?"

The answer is apparently: "If I were to ask you whether the right branch leads to the ruins, would you answer yes?"

I don't quite understand why this question would reveal the correct branch to you. Can someone clear that up for me?