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Year 7

Enlarging objects

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

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New
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Year 7

Enlarging objects

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

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Lesson details

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).

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.
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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Starter quiz

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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

Exit quiz

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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: $$12{1\over2}$$