Well, isn't that a happy little question! If we're looking for a number that rounds to 400 when rounded to the nearest 100, we're searching for a number between 350 and 449. So, any number between 350 and 449 will round to 400 when rounded to the nearest 100. Just remember, there are no mistakes, only happy little accidents!
It rounds to 300
400
It rounds to 400
400
379 rounded to the nearest hundred is 400:)
400
It could be 599, rounded to the nearest 400.
400
400
400
380 rounded to the nearest 10th 400 rounded to the nearest 100th
400