275 ft
Step-by-step explanation:
The formula given to use for the slant height l of the cone is ;
l = (s - πr^2)/π
Now substituting the parameters given in the question, 500 π for area and radius of 15, we have
l = {500π-15^(2)π}/π
l =( 500 π -225 π)/π
l = 275 π/π
l = 275 ft