-52.5% is the change from 40 to 19
Calculation steps:
[( 19 - 40 ) ÷ 40] x 100 = -52.5%
Formula
Percentage change = [(19 - 40) / 40] x 100
Subtract the new number by the original number
19 - 40 = -21
-21 ÷ 40 = -0.525
-0.525 x 100 = -52.5%
Example