877.5% is the change from 40 to 391
Calculation steps:
[( 391 - 40 ) ÷ 40] x 100 = 877.5%
Formula
Percentage change = [(391 - 40) / 40] x 100
Subtract the new number by the original number
391 - 40 = 351
351 ÷ 40 = 8.775
8.775 x 100 = 877.5%
Example