-26.56% is the change from 640 to 470
Calculation steps:
[( 470 - 640 ) ÷ 640] x 100 = -26.56%
Formula
Percentage change = [(470 - 640) / 640] x 100
Subtract the new number by the original number
470 - 640 = -170
-170 ÷ 640 = -0.265625
-0.265625 x 100 = -26.56%