63.68% is the change from 391 to 640
Calculation steps:
[( 640 - 391 ) ÷ 391] x 100 = 63.68%
Formula
Percentage change = [(640 - 391) / 391] x 100
Subtract the new number by the original number
640 - 391 = 249
249 ÷ 391 = 0.6368286445012787
0.6368286445012787 x 100 = 63.68%