-10% is the change from 40 to 36
Calculation steps:
[( 36 - 40 ) ÷ 40] x 100 = -10%
Formula
Percentage change = [(36 - 40) / 40] x 100
Subtract the new number by the original number
36 - 40 = -4
-4 ÷ 40 = -0.1
-0.1 x 100 = -10%
Example