-83.5% is the change from 491 to 81
Calculation steps:
[( 81 - 491 ) ÷ 491] x 100 = -83.5%
Formula
Percentage change = [(81 - 491) / 491] x 100
Subtract the new number by the original number
81 - 491 = -410
-410 ÷ 491 = -0.835030549898167
-0.835030549898167 x 100 = -83.5%