-75% is the change from 40 to 10
Calculation steps:
[( 10 - 40 ) ÷ 40] x 100 = -75%
Formula
Percentage change = [(10 - 40) / 40] x 100
Subtract the new number by the original number
10 - 40 = -30
-30 ÷ 40 = -0.75
-0.75 x 100 = -75%
Example