This is absolutely insane, it will blow your mind.
There is a race between a person and a turtle. The person is obviously a lot faster, so the turtle is given a 100m head start. The runner runs 10 times as fast as the turtle. When the race starts, the person sprints 100m, then he is at the position that the turtle was at the start. By the time he has ran this 100m, the turtle has ran 10m. He continues running and after 10m, he is at where the turtle was at the previous step, and by this time the turtle is 1m ahead. This distance between the runner and turtle continues to decrease by a factor of 10 every time the runner catches up to where the turtle was, and it continues infinitely. Does the runner ever pass the turtle? We know it does in real life, but how? If the runner does, he is completing an infinite number of actions in a finite time...?!?!?!?!