21.43% is the change from 420 to 510
Calculation steps:
[( 510 - 420 ) ÷ 420] x 100 = 21.43%
Formula
Percentage change = [(510 - 420) / 420] x 100
Subtract the new number by the original number
510 - 420 = 90
90 ÷ 420 = 0.21428571428571427
0.21428571428571427 x 100 = 21.43%