-96.25% is the change from 640 to 24
Calculation steps:
[( 24 - 640 ) ÷ 640] x 100 = -96.25%
Formula
Percentage change = [(24 - 640) / 640] x 100
Subtract the new number by the original number
24 - 640 = -616
-616 ÷ 640 = -0.9625
-0.9625 x 100 = -96.25%