33.59% is the change from 640 to 855
Calculation steps:
[( 855 - 640 ) ÷ 640] x 100 = 33.59%
Formula
Percentage change = [(855 - 640) / 640] x 100
Subtract the new number by the original number
855 - 640 = 215
215 ÷ 640 = 0.3359375
0.3359375 x 100 = 33.59%