When rounding a number to the nearest hundred, you look at the digit in the tens place. In this case, the digit in the hundreds place is 4, and the digit in the tens place is 2. Since the digit in the tens place is less than 5, you round down. Therefore, 428 rounded to the nearest hundred is 400.
Well, isn't that a happy little number we have here! When we round 428 to the nearest hundred, it becomes 400. Just imagine that number feeling all snug and cozy, surrounded by those zeros. It's a beautiful thing, my friend.