-85.83% is the change from 642 to 91
Calculation steps:
[( 91 - 642 ) ÷ 642] x 100 = -85.83%
Formula
Percentage change = [(91 - 642) / 642] x 100
Subtract the new number by the original number
91 - 642 = -551
-551 ÷ 642 = -0.8582554517133957
-0.8582554517133957 x 100 = -85.83%