-56.41% is the change from 640 to 279
Calculation steps:
[( 279 - 640 ) ÷ 640] x 100 = -56.41%
Formula
Percentage change = [(279 - 640) / 640] x 100
Subtract the new number by the original number
279 - 640 = -361
-361 ÷ 640 = -0.5640625
-0.5640625 x 100 = -56.41%