-92.34% is the change from 640 to 49
Calculation steps:
[( 49 - 640 ) ÷ 640] x 100 = -92.34%
Formula
Percentage change = [(49 - 640) / 640] x 100
Subtract the new number by the original number
49 - 640 = -591
-591 ÷ 640 = -0.9234375
-0.9234375 x 100 = -92.34%