3
Faces, edges and corners
Discover Mathematics P2: Term 1, Lessons 41–50
GoalCount the faces, edges and vertices of a cube, a box, a pyramid, and describe a cylinder, a cone and a sphere.
New words
face · a flat side of a solid shapeedge · where two faces meetvertex · a corner of a solid shapesolid shape · a shape that is not flat, like a box
Explanation
Solid shapes are not flat. A face is a flat side. An edge is where two faces meet. A vertex is a corner where edges meet. A cube has 6 faces, 12 edges and 8 vertices. A box shape (a rectangular prism) also has 6 faces, 12 edges and 8 vertices. A square-based pyramid has 5 faces, 8 edges and 5 vertices. A cylinder has 2 flat round faces and no vertices. A cone has 1 flat round face and 1 vertex. A sphere has no flat faces, no edges and no vertices.
| Solid | Faces | Edges | Vertices |
|---|---|---|---|
| cube | 6 | 12 | 8 |
| box | 6 | 12 | 8 |
| square pyramid | 5 | 8 | 5 |
Worked examples
A cube, like a dice, has 6 square faces. It has 12 edges and 8 vertices.
A square-based pyramid has 1 square face and 4 triangle faces: 5 faces. It has 8 edges and 5 vertices.
A can of beans is a cylinder. It has 2 flat round faces (top and bottom), a curved side and no vertices.
Class activity
Solid shape hunt. Find a box, a tin can, a ball and a party hat or ice-cream cone in the home. Name each one, then count faces and corners with your finger. Put a small sticker on one corner so you do not count it twice.
Practice
1
How many faces does a cube have?
6 faces.
2
How many vertices does this pyramid have?
5 vertices.
3
A shoe box has how many edges?
12 edges.
4
Name this solid. How many flat faces does it have?
A cone. It has 1 flat face and 1 vertex.
5
Which solid is round all over, with nothing flat on it?
The sphere (a ball).