-5% is the change from 400 to 380
Calculation steps:
[( 380 - 400 ) ÷ 400] x 100 = -5%
Formula
Percentage change = [(380 - 400) / 400] x 100
Subtract the new number by the original number
380 - 400 = -20
-20 ÷ 400 = -0.05
-0.05 x 100 = -5%
Example