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Ch 9.7 Perimeters and Similarity
Learning Target: I will be able to identify and use proportional relationships of similar triangles. Standard 11.0 Students determine how changes in dimensions affect the perimeter of common geometric figures.
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Ch 9.7 Concept
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Ch 9.7 Use a Scale Factor to Find Perimeter If ABCDE ~ RSTUV, find the scale factor of ABCDE to RSTUV and the perimeter of each polygon. Example 4
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Ch 9.7 The scale factor ABCDE to RSTUV is or . AE VU 4 7
Use a Scale Factor to Find Perimeter The scale factor ABCDE to RSTUV is or ___ AE VU __ 4 7 Write a proportion to find the length of DC. Write a proportion. 4(10.5) = 7 ● DC Cross Products Property 6 = DC Divide each side by 7. Since DC AB and AE DE, the perimeter of ABCDE is or 26. Example 4
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Ch 9.7 Use a Scale Factor to Find Perimeter Use the perimeter of ABCDE and scale factor to write a proportion. Let x represent the perimeter of RSTUV. Theorem 7.1 Substitution 4x = (26)(7) Cross Products Property x = 45.5 Solve. Answer: The perimeter of ABCDE is 26 and the perimeter of RSTUV is 45.5. Example 4
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Ch 9.7 If LMNOP ~ VWXYZ, find the perimeter of each polygon.
A. LMNOP = 40, VWXYZ = 30 B. LMNOP = 32, VWXYZ = 24 C. LMNOP = 45, VWXYZ = 40 D. LMNOP = 60, VWXYZ = 45 Example 4
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