-80.71% is the change from 420 to 81
Calculation steps:
[( 81 - 420 ) ÷ 420] x 100 = -80.71%
Formula
Percentage change = [(81 - 420) / 420] x 100
Subtract the new number by the original number
81 - 420 = -339
-339 ÷ 420 = -0.8071428571428572
-0.8071428571428572 x 100 = -80.71%