The rule when rounding off numbers is "If the first figure to be discarded is 5 or more then the previous figure is increased by 1".
When rounding 2451 to the nearest hundred then the first figure to be discarded is 5 therefore the previous figure (the one in front of 5 which is 4 is increased by 1)
So 2451 becomes 2500 when rounded to the nearest hundred.
100
0
97 rounded to the nearest hundred is 100. 97 rounded to the nearest ten is 100
300
2200
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
100
0
300
9000