How many gallons of paint are necessary to paint the walls of a 15' by 12' room with an 8'

Question

ceiling if one gallon of paint covers 80 square feet? (One coat!)

Answer 1

two long walls 2 * 8 * 15 = 240 ft^2
two short walls 2 * 8 * 12 = 192 ft^2
sum = 432 ft^2
432/80 = 5.4 so buy 6 gallons