121 rounded to the nearest 10 is 120 .
200
200
200
200
200
You round it down to 100, as the 2 for tens must be rounded down.
200
200
200
206 rounded to the nearest 100 is 200. Rounded to the nearest ten is 210.
It would be 200 if rounded to the nearest ten and would also be 200 if rounded to the nearest hundred.