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Classifying polygons

Most classrooms have a poster of shapes. Often there is only one example of each shape, with a 'standard' appearance.

  • The triangle is usually acute-angled with a horizontal base.
  • The quadrilaterals, other than kites, usually have one or two horizontal sides and therefore some of them also have vertical sides.
  • The trapezium usually has two (or three) equal sides with the longer side on the base and a shorter side above it.
  • The rectangle usually has the longer side on the base.
  • The pentagon is usually regular, with one side horizontal.
  • The hexagon is usually regular, with a pair of sides horizontal or vertical.
  • All the shapes are convex.

Pattern blocks, which are used frequently in primary classrooms, reinforce this standard perception.

What shape is a baseball 'diamond'? It is a square.

What shape is this?


A trapezium.

You can download the Naming Polygons: Information Sheet, Regular and Irregular Polygons: Information Sheet and the Convex and Non-convex Polygons: Information Sheet which provide more varied examples.

Is this a hexagon?

The hierarchical system used for naming and classifying polygons can cause confusion. For quadrilaterals, the inclusive nature of the definitions can also create misunderstanding.

Pattern block hexagons

This is a practical activity using patterns blocks which encourages students to think more inclusively about hexagons.

Hexagonal tangrams

In this activity, students use a tangram to explore a wide variety of hexagons.

Curriculum links

Year 7: Classify triangles according to their side and angle properties and describe quadrilaterals