New
New
Year 4

Find lines of symmetry in 2D shapes

I can find lines of symmetry in 2D shapes and explain the link between lines of symmetry and number of sides in regular polygons.

New
New
Year 4

Find lines of symmetry in 2D shapes

I can find lines of symmetry in 2D shapes and explain the link between lines of symmetry and number of sides in regular polygons.

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Lesson details

Key learning points

  1. A line of symmetry splits the shape into two equal parts which are mirror images.
  2. Shapes are symmetrical when they look the same when a mirror is placed on the mirror line.
  3. Regular polygons have the same number of lines of symmetry as they have sides.

Keywords

  • Symmetrical - When a shape, pattern or image has one half that is the reflection of the other half, it can be described as symmetrical.

  • Line of symmetry - If you were to fold a shape on its line of symmetry, both halves would match exactly.

  • Regular polygon - A regular polygon has sides that are all equal and angles that are all equal.

Common misconception

Children may not identify lines of symmetry that are neither horizontal nor vertical.

Allow opportunities for children to handle and manipulate cut outs of shapes so that they can try to find lines of symmetry in different orientations. Encourage them to describe the position of the line of symmetry to support their understanding.

This lesson teaches children how to use a mirror to find lines of symmetry. It will be really useful for all children to have access to their own mirror during this lesson.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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6 Questions

Q1.
A __________ is a quadrilateral with two pairs of adjacent sides that are equal in length.
trapezium
Correct answer: kite
hexagon
Q2.
Adjacent means ...
opposite
Correct answer: next to
joining at right angles
Q3.
This kite is also a square. It has lines of symmetry.
An image in a quiz
Correct Answer: 4
Q4.
Look at these rectangles. Which does not show a line of symmetry?
a)
Correct answer: b)
c)
Q5.
Which of these shapes has more than one line of symmetry?
An image in a quiz
Correct answer: a)
b)
c)
Q6.
Which shape has been incorrectly sorted?
An image in a quiz
Correct answer: a)
b)
c)
d)

6 Questions

Q1.
A mirror line is also called the line of __________.
match exactly
Correct answer: symmetry
symmetrical
Q2.
A square is a regular polygon. What is true for all polygons?
They all have 4 sides.
They have two equal sides.
Correct answer: They have all equal sides and all equal angles.
They have a right angle.
Q3.
Match each shape shown to the number of lines of symmetry it has.
An image in a quiz
Correct Answer:pentagon,1

1

Correct Answer:rectangle,2

2

Correct Answer:square,4

4

Q4.
This shape is a regular hexagon. It has lines of symmetry.
Correct Answer: 6
Q5.
The number of lines of symmetry in a regular polygon is __________ the number of sides it has.
less than
Correct answer: equal to
greater than
Q6.
Match the number of lines of symmetry to the shapes.
Correct Answer:square,4 lines of symmetry

4 lines of symmetry

Correct Answer:equilateral triangle,3 lines of symmetry

3 lines of symmetry

Correct Answer:regular pentagon,5 lines of symmetry

5 lines of symmetry

Correct Answer:regular octagon,8 lines of symmetry

8 lines of symmetry

Correct Answer:regular hexagon,6 lines of symmetry

6 lines of symmetry