Final answer:
To lay the footing for Tom's house, approximately 354 bags of concrete will be needed.
Step-by-step explanation:
The footing for Tom's house will run the perimeter of the house, which is a rectangle. The length of the rectangle will be the same as the perimeter of the house, which is given as 200'. The width of the rectangle will be the width of the footing, which is 15". Therefore, the dimensions of the rectangle are 200' for the length and 15" for the width.
To calculate the volume of concrete needed for the footing, we need to convert the dimensions to the same unit. 200' is equal to 2400". The volume of the rectangle can be calculated by multiplying the length, width, and depth together: 2400" * 15" * 9" = 324,000 cubic inches.
Since the volume of concrete needed is in cubic inches, we need to convert it to cubic yards. There are 1728 cubic inches in a cubic foot, and 27 cubic feet in a cubic yard. So, to convert cubic inches to cubic yards, we divide the volume by 1728 and then divide by 27:
324,000 / 1728 / 27 = 7.87 cubic yards of concrete.
If it takes 45 bags of concrete to cover a cubic yard, then we can multiply the number of cubic yards by 45 to find the number of bags needed:
7.87 * 45 = 354.15 bags of concrete.
Therefore, approximately 354 bags of concrete will be needed to lay the footing for Tom's house.