| Fedya always tells the truth, while Vadim always lies. What question should be asked to them so that they give the same answer?

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Recall problem 140.

## Solution

As in problem 140, the question should pertain to a circumstance that is true for one of the boys (for example, Fyodor) and false for the other. There are two such circumstances according to the problem: the name and honesty. Therefore, there can be two simplest questions: "Do you always tell the truth?" or "Is your name Fyodor?" If desired, any of these questions can be complicated indefinitely, for example: "Does your friend tell the truth?", or "Is your friend's name Fyodor?", or "Are you more honest than your friend?" and so on. It is interesting to compare the questions: "Are you more honest than Vadim?" and "Are you more honest than Fyodor?" The boys will answer the first one the same way - "yes," but the second one differently, because Fyodor cannot be more honest than himself and, as an honest person, will admit it.

## Answer

"Is your name Fyodor?"