30.25% is the change from 400 to 521
Calculation steps:
[( 521 - 400 ) ÷ 400] x 100 = 30.25%
Formula
Percentage change = [(521 - 400) / 400] x 100
Subtract the new number by the original number
521 - 400 = 121
121 ÷ 400 = 0.3025
0.3025 x 100 = 30.25%