Question 960317
Wallpaper can turn corners, so consider the entire room is one long wall the length of the perimeter.
P=2(L+W)=2(18'+12')=2(30')=60'
Treat the room as one wall 60 feet long and 10 feet tall. Each 50 foot roll will provide 5 - 10 ft pieces. Since each piece is 2.5 feet wide, we need :
60 feet/2.5 feet per piece=24 pieces
24 pieces/5 pieces per roll= 5 rolls with 1 piece left over
ANSWER:: Boris will need 5 rolls.