-39.81% is the change from 515 to 310
Calculation steps:
[( 310 - 515 ) ÷ 515] x 100 = -39.81%
Formula
Percentage change = [(310 - 515) / 515] x 100
Subtract the new number by the original number
310 - 515 = -205
-205 ÷ 515 = -0.39805825242718446
-0.39805825242718446 x 100 = -39.81%