Enlargement

1
Enlargement
Objectives
C Grade Enlarge a shape by a fractional scale
factor Compare the area of an enlarged shape
with the original shape Find the centre of
enlargement
B Grade Distinguish between formulae for
perimeter, area and volume by considering
dimensions
A Grade Compare areas and volumes of enlarged
shapes Enlarge a shape by a negative scale
factor
Prior knowledge Enlarge an object by a
positive integer scale factor using a centre of
enlargement and ray lines.
2
Enlargement
Enlargement is not just for making an object
bigger using the scale factor
Objects can be enlarged using any number as a
scale factor including fractions and negative
numbers.
Using a scale factor ½ the distance from the CoE
to the image vertices is ½ times the distance
from the CoE to the object vertices.
10 squares right 2 squares down
CoE
Scale Factor ½ Distance from CoE 5 squares right
1 square down
x
x
4 squares right 2 squares down
object
x
4 squares right 6 squares down
Scale Factor ½ Distance from CoE 2 squares right
1 square down
Scale Factor ½ Distance from CoE 2 squares right
3 squares down
This gives us enough information to draw the image
3
Enlargement
Negative scale factors can also be used
A negative scale factor takes the image the
opposite side of the centre of enlargement
Enlarge the object by a scale factor of -2
CoE
4
Enlargement
Enlarge the object by a scale factor of -3
Notice how the image is upside down from the
object
CoE
5
Enlargement
In each case object A has been enlarged to image
B Find the scale factor and centre of enlargement
for
A
A
B
B
A
B
Scale Factor ½
Scale Factor -1
A
6
Enlargement
Worksheet 3
In each case object A has been enlarged to image
B Find the scale factor and centre of enlargement
for
B
A
A
A
B
B
B
A