Heaven and Hell | Puzzles for Interview - Interview Preparation PDF Download

Problem Statement

“You are standing at the gates of heaven and hell. Each gate is guarded by a single guardian. You know that one of the guardians always tells the truth while the other always lies, but you don’t know which one is which. You are allowed to ask only one question to determine which gate leads to heaven, and you can only direct the question to one of the guardians. What question do you ask?”

Solution

The candidate should ask the following question to either of the guardians: “If I were to ask the other guardian which gate leads to heaven, what would he say?”
If the guardian being asked is the truthful one, they will truthfully answer that the lying guardian would indicate the gate to hell. If the guardian being asked is the lying one, they will lie and say that the truthful guardian would indicate the gate to hell.
In either case, the response will be the same, indicating which gate leads to hell. Therefore, the candidate should choose the other gate, which will lead to heaven.

Conclusion

This puzzle is a classic example of a logic problem. It requires the candidate to analyze the situation and come up with a single question that will provide them with the necessary information to make the correct decision. By asking the question in the solution, the candidate can determine which gate leads to heaven and which one leads to hell, regardless of which guardian is telling the truth.