### Home > GC > Chapter 12 > Lesson 12.1.2 > Problem12-20

12-20.

Find the volume of a cone if the circumference of the base is $28\pi$ inches and the height is $18$ inches.

The formula for the circumference of a circle is $2r\pi$.

Find the radius of the base.

Find the area of the base.
Base $= \pi - r^2 = 196\pi$

Find the volume.

The formula for the volume of a cone is $\frac{\text {(area of the base) } \cdot \text{ (height)} }{3}$.

The equation for the lateral surface area of a cone is $\text{LA}=\pi−r−1$