-89.06% is the change from 640 to 70
Calculation steps:
[( 70 - 640 ) ÷ 640] x 100 = -89.06%
Formula
Percentage change = [(70 - 640) / 640] x 100
Subtract the new number by the original number
70 - 640 = -570
-570 ÷ 640 = -0.890625
-0.890625 x 100 = -89.06%