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Warm-up

• Make sure to grab a red pen and be ready to grade your homework

Today

Grade homework Squawk like a CHICKEN!

Discussion Practice problems

7.6: Indirect Measurement and Additional Similarity Theorems

Obj: _______________________ ___________________________

Indirect Measurement

• Measuring the distance of something without physically measuring it

8.5 Indirect Measurement and Additional Similarity Theorems

Key Skills

Use similar triangles to measure distance indirectly.

Estimate the width of the lake.

Finding Distance Indirectly R OCK C

Similar triangles can be used to find distances that are difficult to measure directly.

you walk backward until you can see the top of the wall centered in the mirror. You are 6.5 feet from the mirror and your eyes are 5 feet above the ground.

D B

Not drawn to scale

5 ft

6.5 ft

85 ft

Finding Distance Indirectly

Use similar triangles to estimate the height of the wall.

S OLUTION

DE BA

Ratios of lengths of So, the height of the wall is about 65 feet.

5 = 85 6.5

Substitute.

65.38



Multiply each side by 5 and simplify.

5 ft

6.5 ft

C D

85 ft

Using shadows

• Kim wants to know the height of a basketball hoop. The regulation height is 10 ft. Use Kim’s height and length of the shadows to find the height of the basketball hoop. Is the hoop at regulation height?

• She is 70” and casts a 50” shadow, the basketball hoop casts a 85 ” shadow.

• At a certain time of day, a 6ft man casts a 4 ft shadow. At the same time of day, how tall is a tree that casts an 18 ft shadow?