-68% is the change from 400 to 128
Calculation steps:
[( 128 - 400 ) ÷ 400] x 100 = -68%
Formula
Percentage change = [(128 - 400) / 400] x 100
Subtract the new number by the original number
128 - 400 = -272
-272 ÷ 400 = -0.68
-0.68 x 100 = -68%
Example