20 Aug 2019

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

  • By Connor Whelan  | 
  • 20 Aug 2019  | 
  • 2 min read
  •  |  Free download

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.

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.

Lines of symmetry in a square

An equilateral triangle has 3 lines of symmetry.

Lines of symmetry in a triangle

Primary Maths Dictionary For Parents & Kids

Download our FREE Maths Dictionary For Parents And Kids and find all of the KS2 maths words you'll ever need to know all in one convenient place!

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. 

Lines of symmetry in different shapes


Does your child need help understanding lines of symmetry and the other areas of KS2 maths?

Understanding lines of symmetry can be difficult for children in KS2, but it is important to remember that symmetry only plays a small part in whole maths curriculum! If your child needs more in-depth maths help to raise their attainment and confidence then take a closer look at Matr’s primary maths programmes.

We have different programmes designed for children in all primary year groups, so all that’s left for you to do is find the programme that matches your child’s needs, and then watch their confidence in maths blossom!


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.

Line of symmetry KS2 question

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

Line of symmetry question for children

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

Line of symmetry question

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

Line of symmetry primary school maths


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