Question

A frustum is formed when a plane parallel to a cone’s base cuts off the upper portion as shown.

A cone is shown. The top of the cone is cut off to form a frustum of the bottom portion. The cone has a radius of 3.5 and a height of 8. The frustum has a height of 11 and a radius of 7.5.

Which expression represents the volume, in cubic units, of the frustum?

One-thirdπ(7.52)(11) – One-thirdπ(3.52)(8)
One-thirdπ(7.52)(11) + One-thirdπ(3.52)(8)
One-thirdπ(7.52)(19) – One-thirdπ(3.52)(8)
One-thirdπ(7.52)(19) + One-thirdπ(3.52)(8)

Answer 1

Volume(frustum) = volume(big cone of height 19 and radius 7.5) − volume(small cone of height 8 and radius 3.5).

So the correct expression is: One-third π (7.5^2)(19) − One-third π (3.5^2)(8).