-77.5% is the change from 40 to 9
Calculation steps:
[( 9 - 40 ) ÷ 40] x 100 = -77.5%
Formula
Percentage change = [(9 - 40) / 40] x 100
Subtract the new number by the original number
9 - 40 = -31
-31 ÷ 40 = -0.775
-0.775 x 100 = -77.5%
Example