Pyramids and Cones — Worked Examples

These problems progress from direct volume and surface-area calculations to inverse dimensions, similar cross-sections, centroid interpretation, and oblique-solid checks.

Example 1: Volume of a square pyramid

A square pyramid has base side 6.00 m6.00\,\text{m} and perpendicular height 9.00 m9.00\,\text{m}. Determine its volume.

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Example 2: Slant height and lateral area of a regular square pyramid

A regular square pyramid has base side 8.00 m8.00\,\text{m} and perpendicular height 6.00 m6.00\,\text{m}. Determine its face slant height and lateral area.

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Example 3: Total area of a regular square pyramid

Use the pyramid from Example 2 to determine total surface area.

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Example 4: Volume and slant height of a right circular cone

A right circular cone has radius 3.00 m3.00\,\text{m} and perpendicular height 4.00 m4.00\,\text{m}. Determine its volume and slant height.

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Example 5: Cone lateral and total surface area

For the cone in Example 4, determine its lateral and total surface areas.

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Example 6: Radius from cone volume

A right circular cone must hold 150 m3150\,\text{m}^3 and has perpendicular height 8.00 m8.00\,\text{m}. Determine the required base radius.

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Example 7: Height of a pyramid from volume

A pyramid has base area 45.0 m245.0\,\text{m}^2 and volume 120 m3120\,\text{m}^3. Determine its perpendicular height.

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Example 8: Parallel section inside a cone

A cone has height 15.0 m15.0\,\text{m} and base radius 6.00 m6.00\,\text{m}. Find the radius and area of a section parallel to the base located 9.00 m9.00\,\text{m} from the apex.

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Example 9: Volume of a similar apex cone

For the cone in Example 8, what fraction of the full volume lies between the apex and the section 9.00 m9.00\,\text{m} from the apex?

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Example 10: Centroid of a homogeneous right circular cone

A uniform solid right circular cone is 12.0 m12.0\,\text{m} high. Locate its centroid along the symmetry axis, measured from the base plane.

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Example 11: Oblique pyramid volume

A right pyramid and an oblique pyramid have the same base area B=28.0 m2B=28.0\,\text{m}^2 and the same perpendicular height h=9.00 mh=9.00\,\text{m}. The oblique pyramid has a longer apex-to-base-edge distance. Compare their volumes.

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Example 12: Uniformly scale a cone

A right circular cone has original volume 24.0 m324.0\,\text{m}^3 and total surface area 30.0 m230.0\,\text{m}^2. Every linear dimension is enlarged by factor k=1.50k=1.50. Determine the new volume and total surface area.

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Pyramid and cone calculation check

Volume always uses perpendicular height. Lateral area for a regular pyramid uses the common face slant height, while a right circular cone uses generator length ll. Do not extend these surface-area shortcuts or right-solid symmetry-axis language to arbitrary oblique solids.