30% is the change from 400 to 520
Calculation steps:
[( 520 - 400 ) ÷ 400] x 100 = 30%
Formula
Percentage change = [(520 - 400) / 400] x 100
Subtract the new number by the original number
520 - 400 = 120
120 ÷ 400 = 0.3
0.3 x 100 = 30%
Example