-32.5% is the change from 640 to 432
Calculation steps:
[( 432 - 640 ) ÷ 640] x 100 = -32.5%
Formula
Percentage change = [(432 - 640) / 640] x 100
Subtract the new number by the original number
432 - 640 = -208
-208 ÷ 640 = -0.325
-0.325 x 100 = -32.5%