-79.5% is the change from 400 to 82
Calculation steps:
[( 82 - 400 ) ÷ 400] x 100 = -79.5%
Formula
Percentage change = [(82 - 400) / 400] x 100
Subtract the new number by the original number
82 - 400 = -318
-318 ÷ 400 = -0.795
-0.795 x 100 = -79.5%
Example