31.87% is the change from 640 to 844
Calculation steps:
[( 844 - 640 ) ÷ 640] x 100 = 31.87%
Formula
Percentage change = [(844 - 640) / 640] x 100
Subtract the new number by the original number
844 - 640 = 204
204 ÷ 640 = 0.31875
0.31875 x 100 = 31.87%