[Mathematical logic (other).]

Ilya always tells the truth, but when he was asked the same question twice, he gave different answers. What could this question be?

#
Recall problems 140 and 148.

## Solution

Ilya's second answer differs from the first, which means something has changed. The question itself did not change. What else could have changed besides the question? Only the situation in which this question was asked. Since the problem statement does not mention anything about the location, the person asking, or the air temperature, etc., the properties of the situation that could have changed and can be verified are, firstly, the number of questions already asked to Ilya, and secondly, the time. Therefore, there are two possible questions: "How many questions have I already asked you?" and "What time is it, accurate to the second?" If we allow ourselves to use properties of the situation not mentioned in the problem statement, then there can be as many explanations for the difference in answers as we want. For example, the same question: "Am I a man?" was asked to him first by his father and then by his mother.

## Answer

"How many questions have I already asked you?"