1. Using Similar Figures to Find Missing Lengths
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2. Warm Up Determine if the figures are similar. Explain your answer.
1).
2).
48 in
30°
18 in
15 in
120°
30°
12 in
30°
16 in
35 in
10 in
120°
30°
8 in

3. Warm Up Determine if the figures are similar. Explain your answer.
Yes, corr. angles are equal and corr. sides are proportional.
105 in
1).
2).
48 in
30°
18 in
15 in
120°
30°
12 in
16 in
30°
35 in
10 in
120°
Yes, corr. angles are equal and corr. sides are proportional.
30°
8 in

4. We can use what we know about similar figures to find the missing length of a figure.
5 ft.
2.5 ft.
6 ft. ?

5. Write a proportion using corresponding side lengths.A
15 cm H
5 cm B C J K x
12 cm
Write a proportion using corresponding side lengths.
You can also use scale factor to find the missing length. The smaller triangle is 1/3 the size of the larger triangle.
JK is 4 cm

6. Example 2:
Find the value of x in the following similar figures.
20.5 in E F A
9 in B
10 in x C D G H
X= 4.4 in

7. Indirect Measurement
Example 3: The height of an object and its shadow are proportional to the height of another object and its shadow. Look at the diagram below and find the height of the girl.
10 ft x
4 ft.
8 ft.
The girl is 5 feet tall.

8. 7 cm 1). 15 cm 3). 10 ft. x 6 ft. 7 ft. 4 ft. 3 ft. x 4 ft.
Practice Find the missing length of each set of similar figures. Round to the nearest tenth.
1).
7 cm
2). x
3 in
5 cm
3.5 in
1.4 in x
15 cm
4).
3).
10 ft. x
6 ft.
7 ft.
4 ft.
3 ft. x
4 ft.

9. Practice Find the missing length of each set of similar figures
Practice Find the missing length of each set of similar figures. Round to the nearest tenth.
1).
7 cm
2). x
3 in
5 cm
10.7 cm
3.5 in
1.4 in
7.5 in x
15 cm
4).
3).
10 ft.
6 ft. x
7 ft.
4 ft.
3 ft. x
4 ft.
17.5 ft.
8 ft.

10. Closure
Are all rectangles similar? Give examples and/or non-examples to support your answer.