51.72% is the change from 640 to 971
Calculation steps:
[( 971 - 640 ) ÷ 640] x 100 = 51.72%
Formula
Percentage change = [(971 - 640) / 640] x 100
Subtract the new number by the original number
971 - 640 = 331
331 ÷ 640 = 0.5171875
0.5171875 x 100 = 51.72%