-82.5% is the change from 40 to 7
Calculation steps:
[( 7 - 40 ) ÷ 40] x 100 = -82.5%
Formula
Percentage change = [(7 - 40) / 40] x 100
Subtract the new number by the original number
7 - 40 = -33
-33 ÷ 40 = -0.825
-0.825 x 100 = -82.5%
Example