2700% is the change from 30 to 840
Calculation steps:
[( 840 - 30 ) ÷ 30] x 100 = 2700%
Formula
Percentage change = [(840 - 30) / 30] x 100
Subtract the new number by the original number
840 - 30 = 810
810 ÷ 30 = 27
27 x 100 = 2700%
Example