Five-Minute Check (over Lesson 7
–5)
NGSSS
Then/Now
New Vocabulary
Key Concept: Types of Dilations
Example 1: Identify a Dilation and Find Its Scale Factor
Example 2: Real-World Example: Find and Use a Scale
Factor
Example 3: Verify Similarity after a Dilation

Find the value of a.
A.
1
B.
2
C.
3.5
D.
5
Over Lesson 7
–5
A. A
B. B
C. C
A
0% 0%
B C D

Find the value of n.
A.
45
B.
54
C.
67
D.
76
Over Lesson 7
–5
A. A
B. B
C. C
A
0% 0%
B C D

Find the value of x.
A.
8.5
B.
9
C.
10
D.
11
Over Lesson 7
–5
A
0% 0%
B C
A. A
B. B
C. C
D

Find the value of x.
A.
9
B.
10
C.
11
D.
12
Over Lesson 7
–5
A
0% 0%
B
0%
C
A. A
B. B
C. C
D

Find the value of x.
A.
1
B.
2.4
C.
2.6
D.
4.5
Over Lesson 7
–5
A. A
B. B
C. C
A
0% 0%
B C D

MA.912.G.2.4
Apply transformations to polygons to determine congruence, similarity, and symmetry. Know that images formed by translations, reflections, and rotations are congruent to the original shape. Create and verify tessellations of the plane using polygons.
MA.912.G.2.6
Use coordinate geometry to prove properties of congruent, regular and similar polygons, and to perform transformations in the plane.

You identified congruence transformations.
(Lesson 4
–7)
• Identify similarity transformations.
• Verify similarity after a similarity transformation.

• dilation
• similarity transformation
• center of dilation
• scale factor of a dilation
• enlargement
• reduction

Identify a Dilation and Find Its Scale Factor
A. Determine whether the dilation from Figure A to
Figure B is an enlargement or a reduction. Then find the scale factor of the dilation.
B
is smaller than
A
, so the dilation is a reduction.

Identify a Dilation and Find Its Scale Factor
The distance between the vertices at (2, 2) and (2,
–2) for
A
is 4 and from the vertices at (1, 1) and (1,
–1) for
B
is 2 .
Answer:
So the scale factor is or .
4 2

Identify a Dilation and Find Its Scale Factor
B. Determine whether the dilation from Figure A to
Figure B is an enlargement or a reduction. Then find the scale factor of the dilation.
B
is larger than
A
, so the dilation is an enlargement.

Identify a Dilation and Find Its Scale Factor
The distance between the vertices at (3, 3) for
A
is 6 and (
–3, 3) and from the vertices at (1, 1) and (
–1, 1) for
B
is 2 .
Answer:
So the scale factor is or 3.
2

A.
Determine whether the dilation from Figure A to
Figure B is an enlargement or a reduction. Then find the scale factor of the dilation.
A.
reduction;
2
B.
reduction;
3
C.
enlargement; 2
D.
enlargement; 3
A
0%
A. A
B. B
C. C
B
0%
D. D
C D

B.
Determine whether the dilation from Figure A to
Figure B is an enlargement or a reduction. Then find the scale factor of the dilation.
A.
reduction;
3
B.
reduction;
3
C.
enlargement;
2
D.
enlargement; 2
A
0%
A. A
B. B
C. C
B
0%
D. D
C D

Find and Use a Scale Factor
PHOTOCOPYING A photocopy of a receipt is
1.5 inches wide and 4 inches long. By what percent should the receipt be enlarged so that its image is
2 times the original? What will be the dimensions of the enlarged image?
To enlarge the receipt 2 times the original, use a scale factor of 2. Written as a percent, the scale factor is
(2
●
100%) or 200%. Now, find the dimensions of the enlarged receipt.
width: 1.5 in.
●
200% = 3 in.
length: 4 in.
●
200% = 8 in.
Answer:
The enlarged receipt will be 3 inches by
8 inches.

PHOTOGRAPHS Mariano wants to enlarge a picture he took that is 4 inches by 7.5 inches. He wants it to fit perfectly into a frame that is 400% of the original size. What will be the dimensions of the enlarged photo?
A.
15 inches by 25 inches
A. A
B.
8 inches by 15 inches
B. B
C.
12 inches by 22.5 inches
C. C
0% 0%
D.
16 inches by 30 inches
A
B C D

Verify Similarity after a Dilation
A. Graph the original figure and its dilated image.
Then verify that the dilation is a similarity transformation.
original:
M
(
–6, –3),
N
(6,
–3),
O
(
–6, 6) image:
D
(
–2, –1),
F
(2,
–1),
G
(
–2, 2)
Graph each figure. Since angles,

M


D.
that include

M and

D

M
and

D
are both right
Show that the lengths of the sides are proportional.

Verify Similarity after a Dilation
Use the coordinate grid to find the lengths of the vertical segments
MO
and
DG
and the horizontal segments
MN
and
DF
.
Answer:
Since the lengths of the sides that include

M
and

D
Δ
MNO
are proportional,
~
Δ
DFG
by SAS Similarity.

Verify Similarity after a Dilation
B.
Graph the original figure and its dilated image.
Then verify that the dilation is a similarity transformation.
original:
G
(2, 1),
H
(4, 1),
I
(2, 0),
J
(4, 0) image:
Q
(4, 2),
R
(8, 2),
S
(4, 0),
T
(8, 0)

Verify Similarity after a Dilation
Use the Distance Formula to find the length of each side.

Verify Similarity after a Dilation
Use the Distance Formula to find the length of each side.
Find and compare the ratios of corresponding sides.
Answer:

A.
Graph the original figure and its dilated image.
Then determine the scale factor of the dilation.
original: B(
–7, –2), A(5, –2), D(–7, 7) image: J(
–3, 0), K(1, 0), L(–3, 3)
A.
2
B.
C.
3
A. A
B. B
C. C
2
0% 0%
D.
4
A
B C D

B.
Graph the original figure and its dilated image.
Then determine the scale factor of the dilation.
original: A(4, 3), B(6, 3), C(4, 2), D(6, 2) image: E(6, 4), F(10, 4), G(6, 2), H(10, 2)
A.
2
B.
3
C.
3
A. A
B. B
C. C
A
0% 0%
B
D.
4
C D