Mr. Hensley has a total of 480 square feet of sheet metal with which he would like to construct a cylindrical tank for storing grain. The local zoning law lmits the height of the tank to 13.5 feet. recall that a formula for the surface area of a bottomless cylinder with radius r and height h is A=

Formula for surface area of bottomless cylinder A=pi*r^2+2*pi*r*h=480.

 Given that h=13.5 ft.

3.14r^2+2*3.14*13.5r=480.

3.14r^2+84.78r-480=0.

By solving above quadratic equation

r=4.81, -31.81.

Take r=4.81 as it is only positive quantity.

radius of the cylinder =4.81ft.