Chapter 16: Surface Area and Volume 215
Prisms
First up are polyhedrons, figures made from polygons that meet at their edges. The polygons are
called faces of the polyhedron.
A polyhedron is a solid constructed from polygons that meet at their edges. Each of
the polygons is a face of the polyhedron.
Polyhedrons come in two varieties: prisms and pyramids. A prism is a figure that has a pair of
parallel bases, connected to one another by parallelograms. There’s enough math-speak in that
sentence to scare even the bravest reader, so let’s take it apart and look at some examples. Look
at the book you’re holding. It has rectangles for front and back covers, and those are parallel.
The edges of the pages and the spine of the book form rectangles that connect the front cover
to the back cover. When it’s closed, the book is a prism, specif ically a rectangular prism.
A cube, like a die, is an example of a prism, and a rather special one because all its faces are
squares. Many boxes are good examples. You might have even seen fancy boxes with tops and
bottoms that have six or eight sides. Those are prisms, too, but they’re hexagonal prisms if the bases
have six sides or octagonal prisms if the bases have eight sides. You may have seen a type of candy
that’s packed in a triangular prism. The ends of the box are triangles, and the three sides that
connect the triangles are rectangles.
DEFINITION
A prism is a polyhedron with two parallel faces connected by parallelograms. Prisms
take their names from the polygons that form the bases, such as a rectangle or
octagon. The exception is the cube, which is a prism whose faces are all squares.
Vertices
Edges Faces
