The problem: There’s a box with a hole at each end, and there’s a rabbit in the box. The rabbit sticks his head out of the hole in one end, and a minute later he sticks it out the other end. Half a minute later, his head appears at the opposite end; a fourth of a minute later it appears at the end opposite to that one; an eighth of a minute later, etc., etc. How long will it take before the rabbit sticks its head out of both ends of the box at the same time?

The answer: In theory, two minutes.

In practice, no answer is possible unless you split hares.