Flat shapes around us
A two-dimensional (2D) shape is flat. We can draw it on paper. We name a shape by counting its sides and corners (also called vertices).
- Triangle — 3 sides, 3 corners
- Square — 4 equal sides, 4 corners
- Rectangle — 4 sides, 4 corners
- Pentagon — 5 sides, 5 corners
- Circle — 1 curved side, 0 corners
Worked example
How many sides does a triangle have? Count the straight lines: 1, 2, 3. A triangle has 3 sides and 3 corners.
Making new shapes
We can join shapes to make a picture. Two triangles can fit together to make a square. A rectangle looks like a longer square. A circle has no corners because its edge is one smooth curved line, with no straight sides at all.
Key idea
For shapes with straight sides, the number of corners equals the number of sides.
Remember
- Count sides and corners to name a shape.
- A square has 4 equal sides.
- A circle has no corners.