Tim's mom, Sue, is going to wallpaper his bedroom. Sue goes in and measures Tim's bedroom. She finds that it is 15 feet long, 10 feet wide, and 8 feet tall. She is only going to wallpaper the four walls, not the ceiling and floor of course.

• How much wallpaper does Sue need in order to wallpaper Tim's room?

The answer to this problem is A, 400 squared feet.

Knowing that you are finding the surface area of the four walls you should realize that the answers with cubic are not possible since when you find area you are dealing with two dimensions, so your answer is squared units. That leaves you with the choices of A or D.

To solve this problem it may be best to make a simple drawing of the room and the four walls you need to find the area of.

From your drawing you see that you will need two walls that are 8 feet by 10 feet and the other two walls are 8 feet by 15 feet.

Now find the area of each set of walls.

A = l x w
A = 8 x 10
A = 80 sq. ft.

Since there are two walls like this:

2 x 80 sq. ft. = 160 sq. ft.

The other set of walls:

A = l x w
A = 15 x 8
A = 120 sq. ft.

Since there are two wall like this:

2 x 120 sq. ft. = 240 sq. ft.

To find the total number of square feet Sue needs to buy you add the two areas of the two sets.

160 sq. ft. + 240 sq. ft. = 400 sq. ft.

You now know that Sue has to have at least 400 sq. feet of wallpaper in order to wallpaper Tim's room.