Each inhabitant of a remote village always tells the truth
or always lies. A villager will give only 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 deep 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?
I understand the textbook answer; which is:
“If I were to ask you whether the right branch
leads to the ruins, would you answer yes?”
But my question is if this answer is equally valid:
"Do either of these roads from this fork in the road lead to the ruins?"
Now the reasoning I have is that we know that one of the roads in the fork leads to the ruins. The villager, if he is a liar, will say no. (lie). If he is honest, he will say yes.
Is this sound?
Best Answer
That will tell you whether he’s a liar or not, but you’ll need a second question to determine which fork to take. The textbook answer tells you the right fork, but you’d need a second question to determine whether your informant is a liar. There’s no way to get both pieces of information from a single yes/no question.