Home > Geometric reasoning > Misunderstandings > Classifying polygons

# 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?

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.