A student understands that a face is a flat surface of a three-dimensional solid, an edge is a line segment where two faces meet, and a vertex is a point where edges meet. They can locate and count these features on familiar solids such as cubes, rectangular prisms, pyramids, and other simple shapes, distinguishing faces from curved surfaces and recognizing that these parts describe the solid’s structure.
A face is a flat surface.
An edge is a line segment where two faces meet.
A vertex is a corner point where edges meet.
Example: Count the faces, edges, and vertices of a rectangular prism.
Imagine a box-shaped solid.
Count the faces.
It has a front, back, top, bottom, left, and right face.
So, it has 6 faces.
Count the edges.
Each face has line segments around its sides. Count the box’s edges only once:
So, it has 12 edges.
Count the vertices.
A vertex is a corner of the box. Count:
So, it has 8 vertices.
Therefore, a rectangular prism has:
Remember: a curved surface is not a flat face, and a curved solid may not have straight edges or vertices.
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