Question

A gallon of paint can cover 400 square feet. To the nearest half gallon, find how much paint will be needed to paint two coats on the walls and ceiling of a room that is 20 feet long, 18 feet wide, and 8 feet high. Please do NOT include units, enter a number to the nearest half. Examples, 7, 7.5, 8, 8.5...

Answer 1

You'll need to calculate the surface area to be painted.  The room has two ends, 2 sides and 1 ceiling.  The area of the ceiling is 18*20.  The area of the two ends of the room is 2(8*18).  The area of the two long walls is 2(8*20)

Add these areas together:  18*20 + 2*8*18 + 2*8*20, or 968.

That's 968 square feet.  Since each can contains enough paint for 400 square feet of coverage, divide 968 by 400:

968
----- = 2.42.  This means having to purchase 2.5              (gallons)
400              This answer is accurate to the nearest 0.5.