Question 112496
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+280+168-24-15=649ft^2}}}.  That tells us about one room, but there are 12 rooms on each floor.  So the total surface area for one floor is {{{649*12=7788ft^2}}}.  Now the contractor is getting $.75 per square foot, which is the same as 3/4 dollar, so the cost per floor is {{{(3/4)*7788=$5841}}} dollars.


So if the total amount billed was $17,523, then the contractor must have painted {{{17523/5841=3}}} floors.