-33.75% is the change from 966 to 640
Calculation steps:
[( 640 - 966 ) ÷ 966] x 100 = -33.75%
Formula
Percentage change = [(640 - 966) / 966] x 100
Subtract the new number by the original number
640 - 966 = -326
-326 ÷ 966 = -0.33747412008281574
-0.33747412008281574 x 100 = -33.75%