If I remember correctly, this is a question for admission to a college in China long time ago:

1) You are traveling and have reached a point on the road where it diverges to Path A and Path B. One path leads to Beijing and the other does not.

2) You were told by other people that at this point there is a restaurant boss who always tells the truth, and another restaurant boss who always tells a false statement.

3) You don't know which boss is which. The two bosses know each other and know one always tell the truth and one always tells a false statement.

4) Now you can only ask one question to one boss that you choose, and be able to tell which path is to Beijing. (and it cannot be one question that actually contains two or more questions, and note that it is not one question to each boss, but just a total of one single question) What is that question?


1 Answer 1


I've heard two answers to this question based on if the truth teller has his restaurant in Beijing (everyone in the other village is a liar) and one where the answer has nothing to do with where their restaurants are. The answer to the first form would be:

You ask "Which road leads to your restaurant?". And then you follow that path.
This is because if he tells the truth he will point to his restaurant (Beijing) and if he lies he will have to point to Beijing (as he can't point to his restaurant).

The answer to the second form, which is the standard two guards:

You ask him "which road would the other boss point when I ask 'what path leads to Beijing'?" and follow the other path
The boss who tells the truth would tell you that the liar would point to the path away from Beijing.
The liar would point to the path away from Beijing as he must lie about where the truth boss would point.


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