51.78% is the change from 421 to 639
Calculation steps:
[( 639 - 421 ) ÷ 421] x 100 = 51.78%
Formula
Percentage change = [(639 - 421) / 421] x 100
Subtract the new number by the original number
639 - 421 = 218
218 ÷ 421 = 0.517814726840855
0.517814726840855 x 100 = 51.78%