You have decided to wallpaper your rectangular bedroom. the dimensions are 12 feet 6 inches by 10 feet 6 inches by 8 feet 0 inches high. the room has two windows, each 4 feet by 3 feet and a door 7 feet by 3 feet. determine how many rolls of wallpaper are needed to cover the walls, allowing 10% for waste and matching. each roll of wallpaper is 30 inches wide and 30 feet long. how many rolls of wallpaper should be purchased?

The wall area is the product of the room perimeter and the room height:
   A₁ = (2*(12.5 ft + 10.5 ft))*(8.0 ft) = 368 ft²

The window and door area together is
   A₂ = 2*((4 ft)*(3 ft)) + (7 ft)*(3 ft) = 45 ft²

The area of one roll of wallpaper is
   A₃ = (2.5 ft)*(30 ft) = 75 ft²

Then the number of rolls of wallpaper required will be
   1.1*(A₁ - A₂)/A₃ ≈ 4.74

5 rolls of wallpaper should be purchased.


As a practical matter, not much of the window and door area can be saved. The rolls are 30 inches wide, but the openings are 36 inches wide. Some will likely have to be cut from two strips. The strips will have to be the full length of the wall, and the amount cut likely cannot be used elsewhere. If the window and door area cannot be salvaged, then likely ceiling(5.4) = 6 rolls will be needed (still allowing 10% for matching and waste).