-80% is the change from 405 to 81
Calculation steps:
[( 81 - 405 ) ÷ 405] x 100 = -80%
Formula
Percentage change = [(81 - 405) / 405] x 100
Subtract the new number by the original number
81 - 405 = -324
-324 ÷ 405 = -0.8
-0.8 x 100 = -80%
Example