A new homeowner plans to paint a bedroom, with no paint used on the floor and ceiling. The floor of the room is rectangular 18 feet by 13 feet The walls are 9 feet tall...

Question

A new homeowner plans to paint a bedroom, with no paint used on the floor and ceiling.

1. The floor of the room is rectangular 18 feet by 13 feet
2. The walls are 9 feet tall
3. There is a doorway on one wall that is 3 feet by 7 feet, where no paint is needed.
4. One can of paint can 150 square feet

Assuming the new homeowner needs to apply two coats of paint, what is the minimum number of cans of paint the homeowner needs?

A) 4 cans

B) 8 cans

C) 19 cans

D) 25 cans

Answer 1

Hi Kayla M

B) 8

Since 9 feet is the given height, please let me know if I am correct in assuming 18 ft and 13 ft represent then length and width.

The room you describe room is a Rectangular Prism, look up the formula for the Surface Area of a Rectangular Prism is

SA = 2(l*w + h*w+ l*h)

You should check this formula, draw a picture of the room and since we are given the height 9 feet you need to know which numbers you gave apply to the length and width.

You don’t need all six faces of the rectangular prism in your calculation since the floor and ceiling will not be painted. If you were looking at a rectangular prism you could see that the two faces that do not involve height need not be included. Only the four walls are being painted.

Finally since there will be a door that does not get painted on one wall you need to subtract out the 3 by 7 surface area for the door only once.

SA of the four walls = 2(13*9) + 2(18*9) = 558

SA of the Door = 3*7=21

Area to be painted 558 - 21 = 537 ft²

537 ft²/150 ft² = 3.58 can for one coat: (updated) will need 8 cans since two coats will be applied

I hope this helps