Reductions,%20Enlargements%20and%20the%20Scale%20Factor

1
Reductions, Enlargements and the Scale Factor

• Now if the red square is the original drawing,
  what is the blue square called?
• What is the yellow square called?
• How could we determine how many times bigger the
  blue square is?
• How could we determine how many times smaller
  the yellow square is?
• What do we call that?

2
Reductions, Enlargements and the Scale Factor

• The red square has side lengths of 3.
• The blue square has side lengths of 6.
• So the enlargement has a scale factor of

Side length of scale drawing Side length of
original drawing
which reduces to
3
Reductions, Enlargements and the Scale Factor

• The red square has side lengths of 3.
• The yellow square has side lengths of 1.
• So the reduction has a scale factor of

Side length of scale drawing Side length of
original drawing
4
Reductions, Enlargements and the Scale Factor

• The red square has side lengths of 3.
• The blue square has side lengths of 4.
• The yellow square has side lengths of 2.
• What are the scale factors of each?

Side length of scale drawing Side length of
original drawing
Remember a fraction or decimal is okay
5
Reductions, Enlargements and the Scale Factor

• The red square has side lengths of 3.
• The blue square has side lengths of 4.

• The red square has side lengths of 3.
• The yellow square has side lengths of 2.

Side length of scale drawing Side length of
original drawing
Side length of scale drawing Side length of
original drawing
or
or
6
Reductions, Enlargements and the Scale Factor
A
Triangle ABC needs to be enlarged by a scale
factor of 3. What do we need to do first? What
do we need to do second?
4
5
3
B
C
7
What do you notice about the new drawing? What
about its name? The new triangle is called
________ with side lengths AB _______ BC
_______ AC _______
A
4
5
3
B
C
8
J
Triangle JKL needs to be reduced by a scale
factor of 0.5. What are the new side lengths of
triangle JKL?
9
4
8
K
L
9
J
JK 4 x ________ KL 8 x ________ JL 9
x _________ So Triangle JKL now looks like
this
9
4
8
K
L
10
This picture of a stop sign is a reduction of a
real stop signobviously. It is shown at a scale
factor of 130. The side lengths of the scale
drawing are 25mm. What is the original side
length in cm of an actual stop sign?
STOP
11
What is the original side length in cm of an
actual stop sign? Multiply the side length by the
____________________. 25mm x _____ 750mm Now
convert 750mm to cm. 750mm x 1cm 75cm 10 mm
STOP
12
What is the original side length in cm of an
actual stop sign? 750mm x 1cm ________cm 10
mm So the original side length of the original
stop sign was _________cm.
STOP