-94.69% is the change from 640 to 34
Calculation steps:
[( 34 - 640 ) ÷ 640] x 100 = -94.69%
Formula
Percentage change = [(34 - 640) / 640] x 100
Subtract the new number by the original number
34 - 640 = -606
-606 ÷ 640 = -0.946875
-0.946875 x 100 = -94.69%