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Area and Enlargements

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by

Mr Mattock

on 20 May 2017

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Transcript of Area and Enlargements

Area and Enlargements
Starter
Example
L.O. - To understand the relationship
between the scale factor of an enlargement and the area of the enlarged shape.

(a) What is the scale factor of the enlargement from the small shape to the large.

(b) Find the area of the small shape.

(c) Find the area of the large shape.

(d) How many times bigger is the area of the large shape than the small?
Starter
(a) What is the scale factor of the enlargement from the small shape to the large.
Scale factor 2.

(b) Find the area of the small shape.
1 cm

(c) Find the area of the large shape.
4 cm

(d) How many times bigger is the area of the large shape than the small?
4
2
2
Area Scale Factor
If the length scale factor is B, the area scale factor is B .
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
Area of small shape:


Scale factor of enlargement:


Area of enlarged shape:
Example
Area of small shape:


Scale factor of enlargement:


Area of enlarged shape:
Worked Example
Worked Example
Worked Example
Main Activity
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
Plenary
Area = 36 cm
Area = 9 cm
2 cm
Find the dimensions of the large
rectangle.
Plenary
Area = 36 cm
Area = 9 cm
2 cm
Find the dimensions of the large
rectangle.
4 by 9 rectangle.
Activities
Activity
Answers

Key
Examples
Full transcript