Frustums — Worked Examples

These problems use both direct frustum formulas and similarity reconstruction. Check whether the problem asks for perpendicular height, slant height, capacity, lateral area, total area, or material volume.

Example 1: Volume of a conical frustum

A conical frustum has larger radius R=5.00 mR=5.00\,\text{m}, smaller radius r=3.00 mr=3.00\,\text{m}, and perpendicular height h=6.00 mh=6.00\,\text{m}. Determine its volume.

Step-by-Step Solution

0 of 2 Steps Completed
1

Example 2: Slant height and lateral area of a conical frustum

Use the frustum from Example 1. Determine its slant height and curved lateral area.

Step-by-Step Solution

0 of 2 Steps Completed
1

Example 3: Total closed surface area of a conical frustum

For the frustum in Examples 1–2, determine the total closed surface area.

Step-by-Step Solution

0 of 2 Steps Completed
1

Example 4: Reconstruct the removed cone

A conical frustum has R=6.00 mR=6.00\,\text{m}, r=2.00 mr=2.00\,\text{m}, and height h=8.00 mh=8.00\,\text{m}. Determine the height xx of the small cone removed from the apex and the original full-cone height.

Step-by-Step Solution

0 of 3 Steps Completed
1

Example 5: Verify frustum volume by difference of cones

Use the reconstructed geometry from Example 4 to compute the frustum volume by subtraction.

Step-by-Step Solution

0 of 3 Steps Completed
1

Example 6: Square pyramidal frustum volume

A square pyramidal frustum has lower side 10.0 m10.0\,\text{m}, upper side 6.00 m6.00\,\text{m}, and perpendicular height 9.00 m9.00\,\text{m}. Determine its volume.

Step-by-Step Solution

0 of 2 Steps Completed
1

Example 7: Lateral area of a regular square frustum

Use the square frustum from Example 6. Determine its lateral area.

Step-by-Step Solution

0 of 3 Steps Completed
1

Example 8: Inverse height from conical-frustum capacity

A conical frustum has R=4.00 mR=4.00\,\text{m}, r=2.00 mr=2.00\,\text{m}, and required capacity V=176π m3V=176\pi\,\text{m}^3. Determine the perpendicular height.

Step-by-Step Solution

0 of 2 Steps Completed
1

Example 9: Hollow tapered component material volume

A hollow conical-frustum shell has outer radii Ro=3.00 mR_o=3.00\,\text{m} and ro=2.00 mr_o=2.00\,\text{m}, inner radii Ri=2.70 mR_i=2.70\,\text{m} and ri=1.70 mr_i=1.70\,\text{m}, and common perpendicular height 5.00 m5.00\,\text{m}. Determine the material volume.

Step-by-Step Solution

0 of 3 Steps Completed
1

Example 10: Prismatoidal verification of a conical frustum

For a conical frustum with R=5.00 mR=5.00\,\text{m}, r=3.00 mr=3.00\,\text{m}, and h=6.00 mh=6.00\,\text{m}, verify its volume using the end areas and midpoint area.

Step-by-Step Solution

0 of 3 Steps Completed
1

Example 11: Limiting case as a frustum becomes a cylinder

A conical-frustum formula is evaluated with R=r=4.00 mR=r=4.00\,\text{m} and h=7.00 mh=7.00\,\text{m}. Show that it reduces to the cylinder volume.

Step-by-Step Solution

0 of 2 Steps Completed
1

Example 12: Uniformly scale a frustum

A frustum has volume 40.0 m340.0\,\text{m}^3 and total surface area 55.0 m255.0\,\text{m}^2. A similar frustum is built with every linear dimension multiplied by k=1.80k=1.80. Determine the new volume and area.

Step-by-Step Solution

0 of 2 Steps Completed
1

Frustum calculation check

Confirm that the two bases are parallel and similar before using the direct frustum formula. Use perpendicular height for volume and slant height for lateral area. In hollow components, subtract the inner frustum volume only when the inner and outer geometries are described consistently over the same axial height.