How do we answer this Math Word Problem?

Question

A circular fountain in a park includes a concrete wall that is 3 ft high and 2 ft thick. If the inner radius of the wall is x feet, write an algebraic expression in terms of x that represents the volume of the concrete used to construct the wall. Simplify the expression and write in standard form.

I tried answering but Im not sure if its correct:

The outer radius is x+2

Volume of a cylinder is height.pi.x²

3 pi (x+2)²

3 pi (x² + 4x + 4)

3 pi x² + 12 pi x + 12 pi



Answer 1

You computed the total volume of the cylinder. The question asks for the volume of the concrete.

So subtract the volume of the inner, hollow cylinder:

3*pi*x²

This results in:

12 pi x + 12 pi