What Is A Line Of Symmetry: Symmetrical Shapes Explained For Primary School

In this post we will be answering the question “what is a line of symmetry?” and giving you all of the information you need to help your child understand this small section of the maths curriculum! There are a few practice questions for your child to test their skills, so make sure you scroll all the way to the bottom of the blog.

This blog is part of our series of blogs designed for parents, teachers and carers supporting home learning and looking for home learning resources during the Covid-19 epidemic and beyond.

What is a line of symmetry?

A line of symmetry is a line that cuts a shape exactly in half.  

This means that if you were to fold the shape along the line, both halves would match exactly. Equally, if you were to place a mirror along the line, the shape would remain unchanged. 

A square has 4 lines of symmetry, as shown below.

An equilateral triangle has 3 lines of symmetry.

Lines of symmetry in different symmetrical shapes

Your child will learn all about the different shapes and their respective lines of symmetry, but here are some of the most common shapes. 

When will my child learn about lines of symmetry in primary school?

Children are introduced to symmetry in Year 2, where they should be taught to identify and describe the properties of 2-D shapes, including the number of sides and line symmetry in a vertical line. 

This is then developed in Year 4, where pupils will identify lines of symmetry in 2-D shapes presented in different orientations and complete a simple symmetric figure with respect to a specific line of symmetry. 

The non-statutory guidance also recommends that children recognise line symmetry in a variety of diagrams, including where the line of symmetry does not dissect the original shape.

Symmetrical shapes (lines of symmetry) practice questions

1)  Here is a shape on a grid. Complete the design so that it is symmetrical about the mirror line. Use a ruler.

2) These two shapes are made from equilateral triangles. Draw one line of symmetry on each shape. Use a ruler.

3) Here is a grid with eight squares shaded in. Shade in two more squares to make a symmetrical pattern.

4) The letter D has a line of symmetry. Tick all the other letters that have a line of symmetry.

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