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Year 4

Reflect polygons in a line of symmetry

I can reflect polygons in a line of symmetry, including when there are no sides parallel to the line of symmetry.

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New
New
Year 4

Reflect polygons in a line of symmetry

I can reflect polygons in a line of symmetry, including when there are no sides parallel to the line of symmetry.

Download all resources
Share activities with pupils

Lesson details

Key learning points

  1. When you reflect a shape, it will be the same distance from the mirror line on both sides.
  2. You can reflect a shape by counting the position of each vertex and making a mark, and then joining the marks.

Common misconception

Children may translate or copy a shape rather than 'flipping it' over the line of symmetry.

Use mirrors to support children's understanding of how a shape flips when it is reflected. Explore this idea with a wide variety of shapes.

Keywords

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

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

  • Reflect - When you reflect a shape, you flip it over a mirror line or line of symmetry without turning it or changing the size.

  • Reflection - The mirror image of a shape.

Although children are taught different strategies to reflect shapes in this lesson, they may benefit from using a mirror to support their understanding of reflective symmetry.
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).

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Starter quiz

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6 Questions

Q1.
Which of these shapes are regular polygons?
Correct answer: Equilateral triangle
Rectangle
Correct answer: Square
Trapezium
Q2.
An equilateral triangle has ___ lines of symmetry.
0
1
2
Correct answer: 3
Q3.
This shape is a regular pentagon. It has lines of symmetry.
An image in a quiz
Correct Answer: 5
Q4.
The number of lines of symmetry in a __________ is equal to the number of sides.
quadrilateral
triangle
Correct answer: regular polygon
Q5.
True or false. An isosceles triangle has 3 lines of symmetry.
An image in a quiz
True
Correct answer: False
Q6.
Which statement is true?
Squares and rectangles both have 4 lines of symmetry.
A rectangle has more lines of symmetry than a square.
Correct answer: A square has 4 lines of symmetry, and a rectangle has 2 lines of symmetry.
Squares and rectangles are both regular polygons.

Exit quiz

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6 Questions

Q1.
The mirror image of a shape is a __________ of it.
Correct answer: reflection
larger shape
smaller shape
Q2.
Which image shows a reflection?
a)
Correct answer: b)
c)
Q3.
True or false. This image shows a reflection.
An image in a quiz
True
Correct answer: False
Q4.
Which image shows a reflection?
Correct answer: a)
b)
c)
Q5.
Sam is using vertices to reflect this shape. Which vertex has been placed in the wrong position on the grid?
An image in a quiz
a)
Correct answer: b)
c)
Q6.
Complete the sentence. This image does not show a reflection because __________.
An image in a quiz
The 'reflected' shape is a different size.
Correct answer: The 'reflected' shape is not the same distance from the mirror line.
The 'reflected' shape has not been flipped.