-90.48% is the change from 420 to 40
Calculation steps:
[( 40 - 420 ) ÷ 420] x 100 = -90.48%
Formula
Percentage change = [(40 - 420) / 420] x 100
Subtract the new number by the original number
40 - 420 = -380
-380 ÷ 420 = -0.9047619047619048
-0.9047619047619048 x 100 = -90.48%