Scale Factors
Similar figures have the same shape, but not necessarily
the same size. They are proportional.
Scale Factor
Scale Factor
A scale factor greater than 1 causes the object
to get bigger (scaling up)
A scale factor is a number that relates the two ratios in a
proportion.
A scale factor less than 1 causes the object
to get smaller (scaling down)
It is the number multiplied by or divided by to turn one
ratio into the other.
Find the scale factor from the solid figure to the dashed line
figure:
Take the second figure's measurement and divide it by the first figure's measurement.
4
4
8
Scale Factor:
18
6
Identifying the Scale Factor
To identify the scale factor, write a ratio
(fraction) using one of the dimensions.
Simplify.
Scale Factor:
Scale Factor:
48
24
Actual Size:
66 in
Find the scale factor from the solid figure to
the dashed line figure:
16
actual length
model length
What about the scale factor for height? Will it be
the same?
Scale Factor:
actual height
model height
132 in
Model:
5.5 in
It tells how much larger or smaller the image or object is
11 in
Scale Factors
Using the Scale Factor
Leonardo da Vinci's painting Mona Lisa has dimensions 77 cm by
1 is used to make a small poster. Using
53 cm. A scale factor of 5
the scale factor, find the size of the poster.
77 cm
7 in
A postcard of Vincent Van Gogh's painting Still Life with Irises
Against a Yellow Background has dimensions 7 in and 5 in. The
scale factor for the postcard to the original painting is 4.5. Using
the scale factor, find the size of the actual painting.
Using the Scale Factor
l
l
w
5 in
Scale Factor: 4.5
53 cm
w
1
Scale Factor: 5