Treat "Are you sure?" as a prompt to recheck, not an instruction to reverse your answer. Pause, verify the logic or math, and then either defend the answer or correct it based on what you find.

The interviewer may be pressure-testing your confidence, checking whether you notice an error, or simply asking you to validate an important assumption. You cannot know which in advance.

A strong response is, "Let me quickly check that." Review the critical step. If it still holds, explain why you are comfortable with it. If you find a mistake, correct it directly without over-apologizing.

Practice separating confidence from stubbornness. Keep your answer when the evidence holds; change it when the evidence does not. The case interview guide covers this broader judgment skill.

This question used to make me instantly flip my answer lol. Rechecking first is much better.

If the math still works, I would defend it calmly instead of assuming it is a hint.