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Similar Figures and Perimeter

Similar Figures and Perimeter. Finding a Side Length in Similar Figures. You can set up a proportion between the two shapes and solve using cross products. Let’s Look at an Example. ABC ≈ DEF. E. B. 10. 5. x. 3. A. C. F. D. We can set up a proportion between the two shapes but

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Similar Figures and Perimeter

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  1. Similar Figures and Perimeter

  2. Finding a Side Length in Similar Figures • You can set up a proportion between the two shapes and solve using cross products.

  3. Let’s Look at an Example ABC ≈ DEF E B 10 5 x 3 A C F D We can set up a proportion between the two shapes but need to make sure that we align the corresponding parts If the triangles are similar, the triangle on the right is two times bigger. All of it’s sides will be two times bigger but all of the angles will have the exact same measurement.

  4. ABC ≈ DEF B E x 5 A F C D 8 24

  5. Pentagon ABCDE ≈ FGHIJ • Find the length of side AB A E x 7 I J H 28 B F G 9 D C

  6. You Try x 6 ft 2 ft • A man is 6 ft tall and his shadow is 2 feet long. If a cactus casts a shadow 5 feet long, how tall is it? 5 ft

  7. Your Turn • A telephone pole is 42 feet tall and casts a shadow of 12 feet. If a man standing next to the telephone pole is 7 feet tall, how long is his shadow?

  8. How about this one? 10 x 9 9

  9. You x 4 10 6

  10. Finding Side Lengths Given Perimeter • To find missing side lengths from a perimeter, you must set up an equation and solve for x. Then use your x value to find the side lengths.

  11. Example Perimeter = 35 in 10 in 10 in 2x 2x 3x 15 in 2x + 2x + 3x = 35 7x = 35 x = 5

  12. Perimeter = 72 ft 5x 3x 4x

  13. Perimeter = 46 cm 3x + 3 3x + 3 2x

  14. Putting it all together 26 in 26 in 4x + 1 4x + 1 Perimeter = 39 in 2x + 7 x

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