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      Lesson details

      Learning outcome

      I can enlarge objects using information about the centre of enlargement and scale factor

      Key learning points

      1. Each length in the shape is multiplied by the scale factor
      2. Each vertex in the object is a given distance from the centre of enlargement
      3. This distance is also multiplied by the scale factor to give the distance of the image's vertex

      Keywords

      • Centre of enlargement - The centre of enlargement is the point from which a shape is enlarged.

      • Scale factor - A scale factor is the multiplier between similar shapes that describes how large one shape is compared to the other.

      Common misconception

      Pupils may initially be unsure when enlarging shapes on different background in Q2 of Task B.

      Stress that they can use the same methods as for square or plain backgrounds (e.g. using a ruler, counting units along gridlines).

      Teacher tip

      During the second cycle, the examples only use one method to perform the enlargements. Stress that any of the methods from the first cycle could be used to enlarge the shapes.

      Licence

      This content is © Oak National Academy Limited (2025), 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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      Prior knowledge starter quiz

      6 Questions

      Q1.
      Scale factor is the between similar shapes that describes how large one shape is compared to the other.

      Correct Answer: multiplier, Multiplier

      Q2.
      The invariant point from which an object is enlarged is known as the _________________.

      Correct Answer: centre of enlargement, Centre of enlargement

      Q3.
      P has been enlarged to create A. What is the scale factor?

      An image in a quiz
      $$1\over2$$
      Correct answer: 2
      8
      16

      Q4.
      P has been enlarged to create A. What is the value of $$a$$?

      An image in a quiz
      3
      4
      12
      Correct answer: 16

      Q5.
      P has been enlarged to create B. What is the scale factor?

      An image in a quiz
      Correct answer: $$1\over2$$
      2
      3.5
      7

      Q6.
      P has been enlarged to create B. What is the value of $b$$?

      An image in a quiz
      3.5
      Correct answer: 4
      6

      6 Questions

      Q1.
      Which of these is NOT a method for enlarging an object?

      measuring with a ruler
      Correct answer: counting line length
      counting squares
      marking one point

      Q2.
      When enlarging, an image and object can overlap.

      Correct answer: True
      False

      Q3.
      The shape is being enlarged by a scale factor of $$1\over2$$. The centre of enlargement is marked with a cross. What are the new coordinates of B?

      An image in a quiz
      (16,6)
      (12,6)
      (8,6)
      Correct answer: (7,6)

      Q4.
      When using lines to check the position of the image, the lines must

      Correct answer: go through the centre of enlargement
      go through all of the vertices of the image
      go through all of the vertices of the object
      Correct answer: go through all of the vertices of both object and image

      Q5.
      When enlarging by a non-integer scale factor, the image is always smaller than the object.

      True
      Correct answer: False

      Q6.
      Jun is enlarging an object by a scale factor of $$2{1\over2}$$. If one of the object's lengths is 5, what will the corresponding length be in the image?

      $$2{1\over2}$$
      5
      $$7{1\over2}$$
      Correct answer: $$12{1\over2}$$

      To help you plan your 7 maths lesson on: Enlarging objects, download all teaching resources for free and adapt to suit your pupils' needs...