-21.25% is the change from 400 to 315
Calculation steps:
[( 315 - 400 ) ÷ 400] x 100 = -21.25%
Formula
Percentage change = [(315 - 400) / 400] x 100
Subtract the new number by the original number
315 - 400 = -85
-85 ÷ 400 = -0.2125
-0.2125 x 100 = -21.25%