-98.78% is the change from 820 to 10
Calculation steps:
[( 10 - 820 ) ÷ 820] x 100 = -98.78%
Formula
Percentage change = [(10 - 820) / 820] x 100
Subtract the new number by the original number
10 - 820 = -810
-810 ÷ 820 = -0.9878048780487805
-0.9878048780487805 x 100 = -98.78%