First, we need to find the area of wall we need to cover. The room is 10 by 12 by 8 feet. I'm assuming that we only need to wallpaper the ceiling and side walls. It would be weird to wallpaper the floor when there is carpet/tiling.
Ceiling area: [tex]10 \times 12 = 120[/tex]
Wall area: [tex]2(12 \times 8)+2(10 \times 8)=352[/tex]
Total area: [tex]120+352=472[/tex]
Now, we subtract 15 feet for each window and door. There are two windows and two doors.
[tex]472-4(15)=412[/tex]
412 square feet of wall needs to be wallpapered. Dividing this by 70 (the square footage covered by one roll) gives something a little less than 6.
6 full rolls of wallpaper will be needed to fully wallpaper the room.
