-74.06% is the change from 640 to 166
Calculation steps:
[( 166 - 640 ) ÷ 640] x 100 = -74.06%
Formula
Percentage change = [(166 - 640) / 640] x 100
Subtract the new number by the original number
166 - 640 = -474
-474 ÷ 640 = -0.740625
-0.740625 x 100 = -74.06%