12. The cylinder to the left contains two congruent hollow cones. If the
cylinder's height is 20 inches and its diameter is 14 inches, find the
volume of the solid.

The  volume of the solid is

Step-by-step explanation:

step 1

Find the volume of the cylinder

The volume of the cylinder is given by the formula

we have

---> the radius is half the diameter

substitute the values

step 2

Find the volume of the two congruent hollow cones

The volume of the two cones is given by the formula

we have

---> is the same that the radius of cylinder

----> is half that the height of cylinder

substitute

step 3

To find out the volume of the solid subtract the volume of the two cones from the volume of the cylinder