The answer would be 800 m. This is simple multiplication. If two laps were run on a 400 meter track, we would take those two numbers and multiply. This is because, to put it simply, there are two 400's. So, your answer would be 400 plus 400, or 400 times 2. If you take the zero's off of the 400's, you would get 4 plus 4, or 4 times 4. Since 4 times 4 is 8, 400 times 400 would be 800. Since we have a unit involved, your answer is not 800, it is 800 m. So, your final answer is 800 m.