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      Checking and securing understanding of enlargement with positive fractional scale factors

      Lesson details

      Learning outcome

      I can describe an enlargement and perform a given enlargement on an object.

      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.
      4. A positive fractional scale factor produces an image that is smaller than the original.
      5. To enlarge, you need the centre of enlargement and a scale factor.

      Keywords

      • Transformation - A transformation is a process that may change the size, orientation or position of a shape.

      • Enlargement - Enlargement is a transformation that causes a change of size.

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

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

      Common misconception

      Pupils may measure/count from the object instead of the centre of enlargement.

      Encourage pupils to check their answers by using ray lines.

      Teacher tip

      Discuss what value of a scale factor will make the image smaller than the object and which would make the image larger than the object.

      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.
      __________ will produce an image that is similar to the object.

      Correct answer: An enlargement
      A reflection
      A rotation
      A transformation
      A translaton

      Q2.
      Shape A is enlarged to give shape B. The scale factor of this enlargement is .

      An image in a quiz
      Correct Answer: 4, four

      Q3.
      These two shapes are an enlargement of each other. The missing length is cm.

      An image in a quiz
      Correct Answer: 6, six, 6 cm, 6cm

      Q4.
      Shape A is enlarged to give shape B. The scale factor of this enlargement is .

      An image in a quiz
      Correct Answer: 3, three

      Q5.
      Shape A is enlarged to give shape B. What is the centre of the enlargement?

      An image in a quiz
      (0, 0)
      (3, 3)
      (4, 0)
      (6, 3)
      Correct answer: (6, 4)

      Q6.
      Shape A is enlarged by scale factor 2, centre (-4, 4) to give shape B. Select the points that should be joined to give shape B.

      An image in a quiz
      Correct answer: (0, 0)
      (1, 2)
      Correct answer: (2, 6)
      Correct answer: (6, 2)
      (4, 4)

      6 Questions

      Q1.
      Similar shapes are of each other.

      Correct answer: enlargements
      reflections
      rotations
      transformations
      translations

      Q2.
      Shape B is enlarged to give shape A. What is the scale factor of this enlargement?

      An image in a quiz
      $$4$$
      Correct answer: $$\frac{1}{4}$$
      $$\frac{1}{3}$$
      $$\frac{1}{12}$$

      Q3.
      Which diagram shows a correct enlargement from the marked centre of enlargement?

      An image in a quiz
      An image in a quiz
      Correct Answer: An image in a quiz
      An image in a quiz

      Q4.
      Shape A is enlarged to give shape B. What is the scale factor of this enlargement?

      An image in a quiz
      $$2$$
      $$\frac{2}{3}$$
      Correct answer: $$\frac{3}{2}$$
      $$3$$

      Q5.
      Shape A is enlarged to give shape B. What is the centre of the enlargement?

      An image in a quiz
      (3, 0)
      (4, 0)
      (-1, 4)
      Correct answer: (-3, 4)
      (-3, 3)

      Q6.
      Describe the transformation that maps shape A onto shape B.

      An image in a quiz
      An enlargement scale factor $$\frac{1}{2}$$, centre (-1, 2)
      An enlargement scale factor $$2$$, centre (-1, 2)
      An enlargement scale factor $$2$$, centre (-2, -1)
      Correct answer: An enlargement scale factor $$\frac{1}{2}$$, centre (-2, -1)
      An enlargement scale factor $$\frac{1}{2}$$

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