Question

a cistern will be built out of cement. The walls and bottom will be 1 foot thick. the outer height will be 20 feet. the inner diameter will be 10 feet. to the nearest cubic foot, how much cement will be needed for the job

Answer 1

The volume of cement needed is approximately 1413 cubic feet.

Step-by-step explanation:

To find the amount of cement needed to build the cistern, we need to calculate its volume. The cistern is in the shape of a cylinder, so we can use the formula for the volume of a cylinder, which is V = πr^2h. However, we need to account for the thickness of the walls and bottom, so we need to calculate the inner radius and height of the cistern.

Given that the inner diameter is 10 feet, the inner radius would be half of that, which is 5 feet. The inner height would be the outer height minus twice the thickness of the walls, so it would be 20 - 2(1) = 18 feet.

Plugging these values into the formula, we get V = π(5^2)(18) = 450π cubic feet. To find the amount of cement needed, we need to round this to the nearest whole number. Using π ≈ 3.14, the volume of cement needed is approximately 450(3.14) = 1413 cubic feet.