100
99 itself is a whole number.
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)