-89.5% is the change from 400 to 42
Calculation steps:
[( 42 - 400 ) ÷ 400] x 100 = -89.5%
Formula
Percentage change = [(42 - 400) / 400] x 100
Subtract the new number by the original number
42 - 400 = -358
-358 ÷ 400 = -0.895
-0.895 x 100 = -89.5%
Example