Question

Luke is going to repaint both sides of the door of his room. The door is 36 inches long by 80 inches high. His options at the paint store are below. 1 gallon of paint costs $10 and covers 4,400 square inches of area. 1/2 gallon of paint costs $7 and covers 2,200 square inches of area. If the door requires 2 coats of paint, what is the minimum cost of painting the door of Luke's room?

Answer 1

Alright so since the area of one side of the door is 2,880 inches squared and he wants to paint both sides, you must multiply that by 2.

2880 * 2 = 5760

Since he wants to put 2 coats of paint, this essentially means he wants to paint over everything twice so you must multiply by 2 once more.

5760 * 2 = 11520

This being the total surface area we are going to need to paint. So now we must discover the least amount of money Luke must pay. Knowing we need to cover 11,520 inches worth of door:

4400 * 2 = 8800
8800 + 2200 = 11000
This means we either need to pay another $7 or just buy three gallons.

Best option: Purchase 3 gallons of paint costing 30$


30$