Solid shapes
A three-dimensional (3D) shape is solid. It has length, width and height, so you can hold it, stack it or roll it. Toys, boxes, balls and cans are all 3D shapes.
Parts of a 3D shape
| Part | What it is |
|---|---|
| Face | A flat surface |
| Edge | Where two faces meet |
| Vertex | A corner where edges meet (plural: vertices) |
Some 3D shapes also have a curved surface, like the side of a can.
Common 3D shapes
| Shape | Faces | Edges | Vertices | Real-life example |
|---|---|---|---|---|
| Cube | 6 squares | 12 | 8 | a die, a sugar cube |
| Rectangular prism | 6 rectangles | 12 | 8 | a cereal box, a brick |
| Sphere | 0 (curved surface) | 0 | 0 | a ball, an orange |
| Cylinder | 2 circles + curved surface | 2 (curved) | 0 | a can, a paper towel roll |
| Cone | 1 circle + curved surface | 1 (curved) | 1 | an ice cream cone, a party hat |
| Pyramid | 1 square + 4 triangles | 8 | 5 | the pyramids in Egypt |
Roll, stack or slide?
How a shape moves depends on its surfaces:
- Sphere: rolls in any direction; can’t stack.
- Cylinder: rolls on its side, stacks on its flat faces.
- Cube: slides and stacks, but doesn’t roll.
- Cone: rolls in a circle; can stand on its flat face.
2D faces on 3D shapes
The faces of 3D shapes are 2D shapes. Trace around a cube’s face and you get a square. Trace the bottom of a cylinder and you get a circle. This is a great way to connect 2D and 3D shapes.
Worked examples
Example 1: How many faces does a cube have?
6 square faces.
Example 2: Which 3D shape is a soup can?
A cylinder.
Example 3: Which shapes can roll: cube, sphere, cylinder?
Sphere and cylinder.
Common mistakes
- Calling a 3D shape by its 2D name, like calling a cube a "square" or a sphere a "circle".
- Forgetting the hidden faces at the back and bottom when counting.
- Counting curved surfaces as flat faces.
Try it yourself
- Name a 3D shape that has no faces, edges or vertices.
- How many vertices does a cube have?
- What 2D shape is the bottom of a cone?
- Name something at home shaped like a rectangular prism.
Answers: 1) sphere 2) 8 3) circle 4) e.g. a shoebox
Quick recap
- Three-dimensional shapes are solid.
- They have faces, edges and vertices.
- Cube, sphere, cylinder, cone, pyramid and prism are common 3D shapes.