KS3 Maths · Year 7 · Chapter 2: Geometry · Lesson 4

Enlargements

Year 7About 75 minutesNo calculator47 marks

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Date

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Quick questions to start.

A1
Needed today
Work out $3 \times 2.5$ .
[1 mark]
Answer
A2
Needed today
A rectangle is $4$ cm by $7$ cm. Work out its area.
[1 mark]
Answer
A3
Last lesson
The point $(4, - 1)$ is translated $2$ units left and $5$ units up. Write down its image.
[1 mark]
Answer
A4
From chapter 1
Write $36$ as a product of its prime factors.
[1 mark]
Answer

Year 7

Your teacher works through each example with you. Then try the one beside it.

Example 1

Is rectangle $Q$ an enlargement of rectangle $P$ ? If it is, write down the scale factor.

Not drawn accurately

Hint Divide each side of

Q

by the matching side of

P

. An enlargement needs the same answer both times.

B1
Rectangle $B$ is an enlargement of rectangle $A$ . Work out the scale factor. Show that both pairs of sides give it.
[2 marks]
Not drawn accurately
Answer

Example 2

Enlarge the triangle by scale factor $2$ , centre $C$ . Write down the corners of the image.

Hint Count across and up from

C

to each corner. Double both counts, then count that far from

C

B2
Enlarge the triangle by scale factor $3$ , centre $C$ . Write down the corners of the image.
[2 marks]
Answer

Example 3

Triangle $Y$ is an enlargement of triangle $X$ . Work out $h$ .

Not drawn accurately

Hint Find the scale factor from the pair of sides you know. Then multiply.

B3
$B$ is an enlargement of $A$ . Work out $w$ .
[2 marks]
Not drawn accurately
Answer

Year 7

C1
A triangle has corners $(2, 1)$ , $(- 1, 3)$ and $(0, - 2)$ . It is enlarged by scale factor $3$ with centre the origin $(0, 0)$ . Write down the corners of the image.
[2 marks]
Answer
C2
A rectangle is $5$ cm by $3$ cm. It is enlarged by scale factor $4$ . Work out the perimeter of the image.
[2 marks]
Answer

C3
Rectangle $A$ is $4$ cm by $6$ cm. Which of these is not an enlargement of $A$ ? Give a reason.
$P$ : $8$ cm by $12$ cm, $Q$ : $10$ cm by $15$ cm, $R$ : $12$ cm by $16$ cm
[2 marks]
C4
$B$ is an enlargement of $A$ . Work out the scale factor. Show how you got it.
[2 marks]
Answer

GCSE Foundation

D1
Ben says, "Rectangle $B$ is an enlargement of rectangle $A$ , because every side of $B$ is $3$ cm longer than the matching side of $A$ ."
Ben is wrong. Explain why. Then work out how tall $B$ would need to be, keeping its width of $9$ cm, to be an enlargement of $A$ .
[5 marks]
Not drawn accurately

Stretch

No route is given. The hints are at the end of the sheet. Use one at a time.

Colour one circle on each line.

	Not yet	Nearly	Yes
I can enlarge a shape by a scale factor from a centre.
I can find a scale factor and use it to find a missing length.
I know what an enlargement does to perimeter and to area.

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