900% is the change from 21 to 210
Calculation steps:
[( 210 - 21 ) ÷ 21] x 100 = 900%
Formula
Percentage change = [(210 - 21) / 21] x 100
Subtract the new number by the original number
210 - 21 = 189
189 ÷ 21 = 9
9 x 100 = 900%
Example