50 times 4 is 200, so when you're trying to find what 500 times 400 is, you would keep the 200 and add 4 zeros from the remaining 0's in 500 and 400. I hope that's not too complicated, since this is elementary math.
refer to this picture, it looks complex but it is really pretty easy, im in my last year of high school and i still use this trick to help me on questions like this!! (it will only work if the questions have the same numbers in them like how these two questions both have a 5, 4, and 2, to different places)
