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# Enlargement and Area

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by

## Mr Mattock

on 20 May 2017

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#### Transcript of Enlargement and Area

Enlargement and Area
Starter
Find the area of this rectangle.

Kim says that "If you enlarge the shape by scale factor 2 the area will get 2 times bigger."

What is the width of the enlarged rectangle? What is the length? What is the area? Is Kim correct?
Enlargement and Area
Area Scale Factor
If the length scale factor is B, the area scale factor is B .
L.O. - Understand the effect that enlargement has on area, and find the area of enlarged shapes. (Level 6)
5 cm
7 cm
3 cm
5 cm
What is the area of this rectangle?
If you enlarge the shape by scale
factor 2, what is the length? Width? Area?

What about when you enlarge scale factor 3? 4? 5?
Enlargement and Area
3 cm
5 cm
Scale Enlarged Enlarged Enlarged Area Scale
Factor Length Width Area Factor
2
10 6 60 4
3
4
5
6
Area = 3 x 5 = 15 cm
2
Enlargement and Area
3 cm
5 cm
Scale Enlarged Enlarged Enlarged Area Scale
Factor Length Width Area Factor
2 10 6 60 4
3 15 9 135 9
4 20 12 240 16
5 25 15 375 25
6 30 18 540 36
Area = 3 x 5 = 15 cm
2
2
i.e. if you times the lengths by B you times the area by B .
2
Using the Area Scale Factor
6 cm
7 cm
Area of rectangle =
If the shape is enlarged by scale factor 3 what will be the new area?
Using the Area Scale Factor
6 cm
7 cm
Area of rectangle =
42 cm
If the shape is enlarged by scale factor 3 what will be the new area?
Length scale factor = 3, so area factor = 9.
9 x 42 = 378 cm .
2
2
Example
12 cm
5 cm
Area of Triangle =
(Don't forget to half it).
If the shape is enlarged by scale factor 5, what
will the area of the new shape be?
Example
12 cm
5 cm
Area of Triangle =
(Don't forget to half it).
If the shape is enlarged by scale factor 5, what
will the area of the new shape be?
30 cm
Length scale factor = 5, so Area scale factor = 25.
Area = 30 x 25 = 750 cm
2
2
Main Activity 2
Choose red shapes, amber shapes or green shapes.

Find the area of the shape.

Then find the area of the shape when it is enlarged by the given scale factor.
Area = 9 Area = 24 Area = 35 Area = 25
Enlarged = 36 Enlarged = 216
Enlarged = 560 Enlarged = 2500
Area = 35 Area = 30 Area = 70 Area = 28
Enlarged = 560 Enlarged = 750
Enlarged = 700 Enlarged = 7
Area = 64 Area = 12 Area = 20 Area = 0.25
Enlarged = 1024 Scale factor = 3
Enlarged = 5 Enlarged = 0.4375
= 9/16
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