Percent increase is ~81.8%
To find the percent change from 275 to 500, subtract 275 from 500. You will have 225. 
To find the percentage you set up a cross multiply equation 
X.      225
—- X —-
100.    275
 Then you will have
275x = 22500 
Where x= 81.8~
Where 500 is ~181.8% of 275