The percent increase from April to May is 30%.
In order to find this we must use the percent change formula. It is listed below.
(New - Old)/Old *100 = Percent Change
Now we can plug in known values to determine the percent change.
(390 - 300)/300 * 100 = Percent Change
90/300 * 100 = Percent Change
.30 * 100 = Percent Change
30% = Percent Change