-80% is the change from 505 to 101
Calculation steps:
[( 101 - 505 ) ÷ 505] x 100 = -80%
Formula
Percentage change = [(101 - 505) / 505] x 100
Subtract the new number by the original number
101 - 505 = -404
-404 ÷ 505 = -0.8
-0.8 x 100 = -80%
Example