Well, isn't that a happy little question! Let's see, when we round 721 to the nearest hundred, we look at the digit in the tens place - which is 2. Since 2 is less than 5, we round down, so 721 rounded to the nearest hundred is 700. Just a little adjustment to make our number feel perfectly balanced and harmonious.
700
100
0
97 rounded to the nearest hundred is 100. 97 rounded to the nearest ten is 100
720
700
800
721
853 rounded to the nearest 100: 900. 10853 rounded to the nearest 100: 10900.
100
100
0
555 rounded to the nearest 100 is 600.
97 rounded to the nearest hundred is 100. 97 rounded to the nearest ten is 100
100
100
720