51.3% is the change from 423 to 640
Calculation steps:
[( 640 - 423 ) ÷ 423] x 100 = 51.3%
Formula
Percentage change = [(640 - 423) / 423] x 100
Subtract the new number by the original number
640 - 423 = 217
217 ÷ 423 = 0.5130023640661938
0.5130023640661938 x 100 = 51.3%