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Year 4

Reflect polygons that are dissected by the line of symmetry

I can reflect polygons that are dissected (cut in half) by the line of symmetry, and explore the new shapes that are created when a polygon is reflected.

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New
New
Year 4

Reflect polygons that are dissected by the line of symmetry

I can reflect polygons that are dissected (cut in half) by the line of symmetry, and explore the new shapes that are created when a polygon is reflected.

Download all resources
Share activities with pupils

Lesson details

Key learning points

  1. When you reflect a shape, each vertex will be the same distance from the line of symmetry.
  2. When you reflect a polygon that has a side that is touching the mirror line, you can sometimes create a new shape.

Common misconception

Children may miscount the number of squares from the mirror line when plotting each vertex to reflect the shape.

Encourage children to work systematically by only marking one vertex at a time to reduce the chance of errors. Also encourage use of mirrors to check.

Keywords

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

  • Mirror line - Mirror line is another term to describe the line of symmetry.

  • 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 reflection of a shape is the mirror image of a shape.

Although this lesson has been designed to teach other strategies for reflecting in a line of symmetry, children may benefit from being able to use mirrors 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.
The reflection of a shape is sometimes called a __________.
Correct answer: mirror image
copy
different 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?
a)
b)
Correct answer: c)
Q5.
Sam is using vertices to reflect this shape. Which vertex is in the wrong position on the grid?
An image in a quiz
a
b
Correct answer: c
Q6.
Complete the sentence. This image does not show a reflection because __________
An image in a quiz
the shape is a different size.
the shape is not the same distance from the mirror line.
Correct answer: the shape has not been flipped over the mirror line.

Exit quiz

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6 Questions

Q1.
This shape has been reflected. Each vertex is __________ from the line of symmetry.
An image in a quiz
a greater distance
a lesser distance
Correct answer: the same distance
Q2.
Which of these images shows a correct reflection?
a)
Correct answer: b)
c)
Q3.
Which of these images shows a correct reflection?
a)
b)
Correct answer: c)
Q4.
Which of these images is not a correct reflection?
Correct answer: a)
b)
c)
Q5.
Here are are three different triangles that have been reflected in the line of symmetry. Name the new shapes that have been made.
An image in a quiz
Correct Answer:a),triangle

triangle

Correct Answer:b),square

square

Correct Answer:c),kite

kite

Q6.
True or false. When you reflect a rectangle that has a side that touches the mirror line, it will create a larger rectangle.
An image in a quiz
Correct answer: True
False