Edges, vertices, and faces
Identify and describe properties of 3-D shapes including the number of edges, vertices, and faces
What a learner can do afterwards
- Count the edges, vertices, and faces of common 3-D shapes
- Use the terms edge, vertex (vertices), and face correctly
- Describe a 3-D shape by its properties (e.g. a cube has 6 faces, 12 edges, 8 vertices)
The lesson
A 3-D shape like a cube has three special parts. A face is a flat side you can touch, like the front of a book. An edge is the straight line where two faces meet. A vertex is the sharp point where edges meet. When there is more than one, we call them vertices.
Look at a cube, like a dice. It has 6 flat faces, and every face is a square. It has 12 edges where the faces meet. It has 8 vertices, the sharp corners.
When you count edges or vertices on a shape, touch each one only once. If you touch the same corner twice, your count will be wrong.
A triangular prism looks like a tent. It has 2 triangle faces and 3 rectangle faces, so 5 faces in all. It has 9 edges and 6 vertices.
Faces are flat, edges are the lines where faces meet, and vertices are the corners. Count each part just once.
Watch it
Where it sits
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.