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Illustrative Math
Grade 8
Let’s find missing side lengths in triangles.
Illustrative Math Unit 8.2, Lesson 9 (printable worksheets)
The following diagram shows how to decide if two triangles are similar by looking at quotients of lengths of corresponding sides.
Triangle A has side lengths 2, 3, and 4. Triangle B has side lengths 4, 5, and 6. Is Triangle A similar to Triangle B?
Your teacher will assign you one of the three columns in the second table.
Triangle ABC is similar to triangles DEF, GHI, and JKL. The scale factors for the dilations that show triangle ABC is similar to each triangle are in the table.
Triangles ABC and DEF are similar. Explain why AB/BC = DE/EF.
Triangles ABC, EFD, and GHI are all similar. The side lengths of the triangles all have the same units. Find the unknown side lengths.
The Open Up Resources math curriculum is free to download from the Open Up Resources website and is also available from Illustrative Mathematics.
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