-40.63% is the change from 640 to 380
Calculation steps:
[( 380 - 640 ) ÷ 640] x 100 = -40.63%
Formula
Percentage change = [(380 - 640) / 640] x 100
Subtract the new number by the original number
380 - 640 = -260
-260 ÷ 640 = -0.40625
-0.40625 x 100 = -40.63%