SOLUTION: please help me on this problem! A contractor has been assigned the job of painting the rooms of an office building. Each floor of the building has 12 identical rooms that need to

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Question 112496: please help me on this problem!
A contractor has been assigned the job of painting the rooms of an office building. Each floor of the building has 12 identical rooms that need to be painted. The four walls and the ceiling of each room will be painted. Each room is 12 ft. by 14 ft. and has a height of 10 ft.One wallhas a door with dimensions of 8 ft. by 3 ft. and another wall has a window that is 5 ft. by 3 ft. If the contractor charged $0.75 per square foot for labor and paint,how many floors were painted if the bill was $17,523?

Answer by solver91311(24713) About Me  (Show Source):
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Ok, to begin with, you have a room that is 12 by 14 by 10. Two of the walls are 12 X 10 or 120 square feet each times 2 for 240 square feet, the other two walls are 14 by 10 or 140 square feet each times 2 for 280 square feet, and one ceiling that is 12 by 14 or 168 square feet. Furthermore you have to subtract the area of the 8 by 3 door, or 24 square feet and the 5 by 3 window or 15 square feet. So the total surface area to be painted in each room is 240%2B280%2B168-24-15=649ft%5E2. That tells us about one room, but there are 12 rooms on each floor. So the total surface area for one floor is 649%2A12=7788ft%5E2. Now the contractor is getting $.75 per square foot, which is the same as 3/4 dollar, so the cost per floor is %283%2F4%29%2A7788=%245841 dollars.

So if the total amount billed was $17,523, then the contractor must have painted 17523%2F5841=3 floors.