The "square feet" that the paint covers refers to the area of the billboard. If the billboard is 30 x 18, then its area is those 2 numbers multiplied together. The area of the billboard is 540. If one gallon of paint covers 250 square feet, then we need 540/250 gallons, which is 2.16. If you have to buy the paint by the gallon, then you will need 3 because you are going to use .16 of a third gallon.
