Out of the box thinking.

If A is 15cm away form a wall, and moves by dividends of 2, etc it would move 7cm, then 3.5, then 1.75, then 0.875, etc. Will it ever reach the wall? Before you answer "no" think about it.

You know, if the time it takes to move 1 dividend is constant, then A will never reach the wall. Unless you take into account whether space is quantized and shit like that.