37.5% is the change from 640 to 880
Calculation steps:
[( 880 - 640 ) ÷ 640] x 100 = 37.5%
Formula
Percentage change = [(880 - 640) / 640] x 100
Subtract the new number by the original number
880 - 640 = 240
240 ÷ 640 = 0.375
0.375 x 100 = 37.5%
Example