21.25% is the change from 640 to 776
Calculation steps:
[( 776 - 640 ) ÷ 640] x 100 = 21.25%
Formula
Percentage change = [(776 - 640) / 640] x 100
Subtract the new number by the original number
776 - 640 = 136
136 ÷ 640 = 0.2125
0.2125 x 100 = 21.25%