Agallon of paint covers about 300 square feet of a wall. shani plans to paint all the walls and ceiling of a rectangular room the same color. the room measures 15 feet wide, 20 feet long, and 8 feet high. how many gallons of paint will shani need to put two coats of paint on the ceiling and walls?

Find the surface area of the room by measuring all the areas of the 6 surfaces. This is simple, as each side is repeated, therefore you only need to do 3 equations. But since you don't need to measure the floor, you only need to do the first one once.
15*20 =  300
20*8*2 = 320
8*15*2 = 240
Add all these up to get 860, then multiply it by 2 to get your second coat of paint, which will equal 1,720.
Now you divide that by  300, getting 5.73 gallons of paint required to paint the ceiling and walls.