28% is the change from 500 to 640
Calculation steps:
[( 640 - 500 ) ÷ 500] x 100 = 28%
Formula
Percentage change = [(640 - 500) / 500] x 100
Subtract the new number by the original number
640 - 500 = 140
140 ÷ 500 = 0.28
0.28 x 100 = 28%
Example