-49.9% is the change from 501 to 251
Calculation steps:
[( 251 - 501 ) ÷ 501] x 100 = -49.9%
Formula
Percentage change = [(251 - 501) / 501] x 100
Subtract the new number by the original number
251 - 501 = -250
-250 ÷ 501 = -0.499001996007984
-0.499001996007984 x 100 = -49.9%