1010% is the change from 90 to 999
Calculation steps:
[( 999 - 90 ) ÷ 90] x 100 = 1010%
Formula
Percentage change = [(999 - 90) / 90] x 100
Subtract the new number by the original number
999 - 90 = 909
909 ÷ 90 = 10.1
10.1 x 100 = 1010%
Example