Published over 1 year ago by Ann Baker

*This time, I have chosen this 2D shape as a discussion starter*.

There are many misconceptions our students can develop as a direct result of the limited opportunities we give students to meaningfully consider the properties and orientation of 2D shapes.

We need to explore what students are thinking and will often founded error are **founded on faulty assumptions or knowledge**. For instance, I have met students who have serious misconceptions about what a shape actually is.

One such misunderstanding is that a four-sided shape such as the following is not actually a 'shape' ...

And then there are fixed definition misconceptions, such as students telling me that hexagons, octagons or pentagons must have sides of all the same length. They appear to have no idea about irregular shapes.

Similarly I have had students use their limited understanding to tell me that each of the following are triangles.

In these instances, students are **using only partial information**. In the latter case that information is based on 'the pointy bit' to make the judgement.

Use this 'Does it Matter' as a warm up, discussion starter or strategy lesson.

Download a PDF version here: DiM2 Shape 3dl

Ask students to share with a partner which shapes might belong together and **to say why**.

Initial responses might just join the obvious pairs so if necessary 'push' for some creativity and critical thinking, for instance you might say, 'I think the two triangles and the regular hexagon go together. Why might I think that?’

For more stretch, ask 'Can you find more than three ways to sort?' or 'Can you explain each 'sort'?'

Some ideas could include:

- number of sides
- right angles, no right angles
- line of symmetry, no line of symmetry
- will tessellate
- concave parts / no concave parts
- sum of the internal angles
- could be made by covering with one of the other shapes
- all angles in the shape are identical, different.

**Note**: there are many possibilities and some may come from left field, so remember to encourage respectful listening and sharing of ideas. You may need to model some responses, e. g. 'yes, I never thought of that before' or 'can you please explain that again so that I can think about it some more?'

And another, for a Follow up lesson to use in the same way:

Download a PDF version here: DiM2 Shape 4dl

By now I'd hope you're seeing much more accuracy in identification, more vocabulary use and greater confidence. Have fun!

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