-90.32% is the change from 310 to 30
Calculation steps:
[( 30 - 310 ) ÷ 310] x 100 = -90.32%
Formula
Percentage change = [(30 - 310) / 310] x 100
Subtract the new number by the original number
30 - 310 = -280
-280 ÷ 310 = -0.9032258064516129
-0.9032258064516129 x 100 = -90.32%