100
When rounding 9.9 to the nearest whole number, you look at the digit immediately to the right of the decimal point, which is 9 in this case. Since 9 is equal to or greater than 5, you round up the whole number. Therefore, 9.9 rounded to the nearest whole number is 10.
It can be rounded to 99 or 98.6
100
It is 99.
99 x 10 - 99 x 9 = 99(1 x 10 - 1 x 9) = 99(10 - 9) = 99(1) =99
99 rounded to the nearest tens place is 100
98.6m rounded to the nearest meter is 99 meters.
9.9
100
It is 99.
9.94987 (rounded)