-17.81% is the change from 511 to 420
Calculation steps:
[( 420 - 511 ) ÷ 511] x 100 = -17.81%
Formula
Percentage change = [(420 - 511) / 511] x 100
Subtract the new number by the original number
420 - 511 = -91
-91 ÷ 511 = -0.1780821917808219
-0.1780821917808219 x 100 = -17.81%