-83.96% is the change from 505 to 81
Calculation steps:
[( 81 - 505 ) ÷ 505] x 100 = -83.96%
Formula
Percentage change = [(81 - 505) / 505] x 100
Subtract the new number by the original number
81 - 505 = -424
-424 ÷ 505 = -0.8396039603960396
-0.8396039603960396 x 100 = -83.96%