-40% is the change from 285 to 171
Calculation steps:
[( 171 - 285 ) ÷ 285] x 100 = -40%
Formula
Percentage change = [(171 - 285) / 285] x 100
Subtract the new number by the original number
171 - 285 = -114
-114 ÷ 285 = -0.4
-0.4 x 100 = -40%
Example