-52.34% is the change from 640 to 305
Calculation steps:
[( 305 - 640 ) ÷ 640] x 100 = -52.34%
Formula
Percentage change = [(305 - 640) / 640] x 100
Subtract the new number by the original number
305 - 640 = -335
-335 ÷ 640 = -0.5234375
-0.5234375 x 100 = -52.34%