-55.56% is the change from 90 to 40
Calculation steps:
[( 40 - 90 ) ÷ 90] x 100 = -55.56%
Formula
Percentage change = [(40 - 90) / 90] x 100
Subtract the new number by the original number
40 - 90 = -50
-50 ÷ 90 = -0.5555555555555556
-0.5555555555555556 x 100 = -55.56%