-30.94% is the change from 640 to 442
Calculation steps:
[( 442 - 640 ) ÷ 640] x 100 = -30.94%
Formula
Percentage change = [(442 - 640) / 640] x 100
Subtract the new number by the original number
442 - 640 = -198
-198 ÷ 640 = -0.309375
-0.309375 x 100 = -30.94%