A gallon of enamel paint can cover 300 square feet. Find how many gallon containers of paint should be bought to paint three coats on a wall measuring 21 by 8 feet.

Answer 1

This is a real-world problem whose answer should be the number of containers rather than gallons. Find the area of the wall by multiplying its dimensions (8 x 21 = 168) then multiply that by the number of coats (3 x 168 = 504 square feet). One container of paint will leave (504 - 300) 204 square feet needing more paint so you need another container for a total of 2.

Answer 2

One gallon of paint covers 300 square feet.

The wall you need to paint is 21 * 8 feet.

21 feet * 8 feet = 168 square feet.

You need to paint 168 square feet three times because you need three coats of paint.

3 coats of paints * 168 square feet = 504 square feet

Cross multiply: 300 square feet / 1 gallon = 504 square feet / x gallons

300x = 504(1)

x = 504 / 300

x = 1.68 gallons of paint.

In other words, it takes 1 gallon of paint to cover 300 square feet while it takes 1.68 gallons to cover 504 square feet.