-82.16% is the change from 510 to 91
Calculation steps:
[( 91 - 510 ) ÷ 510] x 100 = -82.16%
Formula
Percentage change = [(91 - 510) / 510] x 100
Subtract the new number by the original number
91 - 510 = -419
-419 ÷ 510 = -0.8215686274509804
-0.8215686274509804 x 100 = -82.16%