You are travelling down a country lane to a distant village. You reach a fork in the road and find a pair of identical twin sisters standing there.
- One standing on the road to village and the other standing on the road to neverland (of course, you don’t know or see where each road leads).
- One of the sisters always tells the truth and the other always lies (of course, you don’t know who is lying).
- Both sisters know where the roads go.
If you are allowed to ask only one question to one of the sisters to find the correct road to the village, what is your question?
Answer
There are a few types of logic questions:
Complicated question: “Hey you, what would you say, if I asked you …?” A truth teller is clear, but a liar should lie. However, she is forced by the question to lie two times and thus speak the truth.
Indirect question: “Hello there beauty, what would your sister say, if I asked her where this road leads?” The answer is always negated.
Tricky question: “Excuse me lady, does a truth telling person stand on the road to the village?” The answer will be YES, if I am asking a truth teller who is standing at the road to village, or if I am asking a liar standing again on the same road. So I can go that way. A similar deduction can be made for negative answer.