# regular pyramid

## Volume of regular tetrahedron of given length of edges

**Problem**

Determine the volume of a regular tetrahedron of edge 2 ft.

A. 1.54 ft^{3} |
C. 1.34 ft^{3} |

B. 1.01 ft^{3} |
D. 0.943 ft^{3} |

## Volume of pyramid cut from a sphere

**Problem**

The diameter of a sphere is 18 in. Find the largest volume of regular pyramid of altitude 15 in. that can be cut from the sphere if the pyramid is (a) square, (b) pentagonal, (c) hexagonal, and (d) octagonal.

## 016 Radius of the sphere circumscribing a regular triangular pyramid

**Example 016**

Find the area of the surface and the volume of the sphere circumscribed about a regular tetrahedron of edge 25 cm. See Figure 015.

## The Regular Tetrahedron

Regular tetrahedron is one of the regular polyhedrons. It is a triangular pyramid whose faces are all equilateral triangles.