Question

A gallon of latex paint can cover 500 square feet. Maria has a rectangular room whose dimensions are 21 feet by 22 feet, with 9-foot ceilings. How many gallon containers of paint does she need to buy to paint two coats on each wall?

Answer 1

The wall area would be (9 ft) [ (2) (21 ft) + (2) (22 ft) ]

Simplifying, A = Area = 9(42+44) ft^2 = 774 square feet.

You did not share info regarding how many square feet of all a gallon container will cover. Let us for example purposes only suggest that each gallon will cover 400 square feet.

Then:

774 sq ft 1 gal
------------- * --------------- * 2 coats = 3.87 gal. Round this up to 4 gal.
1 400 sq ft