7.97% is the change from 640 to 691
Calculation steps:
[( 691 - 640 ) ÷ 640] x 100 = 7.97%
Formula
Percentage change = [(691 - 640) / 640] x 100
Subtract the new number by the original number
691 - 640 = 51
51 ÷ 640 = 0.0796875
0.0796875 x 100 = 7.97%