You round it down to 100, as the 2 for tens must be rounded down.
To the nearest ten, 120 To the nearest hundred, 100
121 rounded to the nearest 10 is 120 .
It is 300 when rounded to the nearest hundred
916 rounded to the nearest hundred is 900
87.3809 is already rounded to the nearest hundred thousandths. 87.3809 rounded to the nearest thousand is 87.381.
0
0
0
678 is rounded nearest hundred is 700
300
800