-42.5% is the change from 40 to 23
Calculation steps:
[( 23 - 40 ) ÷ 40] x 100 = -42.5%
Formula
Percentage change = [(23 - 40) / 40] x 100
Subtract the new number by the original number
23 - 40 = -17
-17 ÷ 40 = -0.425
-0.425 x 100 = -42.5%
Example