-27.5% is the change from 40 to 29
Calculation steps:
[( 29 - 40 ) ÷ 40] x 100 = -27.5%
Formula
Percentage change = [(29 - 40) / 40] x 100
Subtract the new number by the original number
29 - 40 = -11
-11 ÷ 40 = -0.275
-0.275 x 100 = -27.5%
Example