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Grade 10 Similar Triangles & Scale Factor Worksheet with Answers

Grade 10 (US) · Year 11 (UK) · Class 10 (India) · Math

Unit 3: TrianglesSimilarityCCSS G-SRT.B.5

Using scale factors and proportions to find missing sides, perimeters and areas of similar figures. This free high school worksheet has 12 questions and a full answer key. Print it or save it as a PDF — every answer is checked by code, not guessed.

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Similar Triangles & Scale Factor

Grade 10 · Math

Score___ / 12

Name

Class

Date

Learning goal: Similarity · CCSS G-SRT.B.5

Directions: Use the pictures to help you. Solve each problem. Show your work, then write your answer in the box.

Example

Triangle ABC ~ triangle DEF. AB = 9, BC = 12, DE = 27. Find EF.

Answer: 36

RememberScale and similar figures

1
Triangle ABC ~ triangle DEF. AB = 7, BC = 24, DE = 35. Find EF.
Answer
2
Triangle ABC ~ triangle DEF. AB = 5, BC = 12, DE = 10. Find EF.
Answer
3
Triangle ABC has sides 6, 8, 10. A similar triangle has sides 24, 32, 40. What is the scale factor from ABC to the larger triangle?
Show your work
Answer
4
Two similar triangles have a scale factor of 5. The smaller one has perimeter 56. What is the perimeter of the larger one?
Show your work
Answer
5
Two similar triangles have a scale factor of 5. The smaller one has perimeter 30. What is the perimeter of the larger one?
Show your work
Answer
6
Triangle ABC has sides 9, 12, 15. A similar triangle has sides 36, 48, 60. What is the scale factor from ABC to the larger triangle?
Show your work
Answer
7
Two similar triangles have a scale factor of 4. The smaller one has perimeter 12. What is the perimeter of the larger one?
Show your work
Answer
8
Two similar triangles have a scale factor of 3. The smaller one has perimeter 24. What is the perimeter of the larger one?
Show your work
Answer
9
Two similar triangles have a scale factor of 2. The smaller one has perimeter 36. What is the perimeter of the larger one?
Show your work
Answer
10
Triangle ABC ~ triangle DEF. AB = 8, BC = 15, DE = 32. Find EF.
Answer
11
Triangle ABC ~ triangle DEF. AB = 5, BC = 12, DE = 20. Find EF.
Answer
12
Triangle ABC has sides 3, 4, 5. A similar triangle has sides 6, 8, 10. What is the scale factor from ABC to the larger triangle?
Show your work
Answer

★ Challenge corner for fast finishers

A circle fits exactly inside a square of side 5 (touching all four sides). What is the area of the circle in terms of π?

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Teacher's comments

Free printable worksheets with answer keys · aethelsystems.com/worksheets/math/10/similar_triangles

Answer key (click to show)

1.120
2.24
3.4
4.280
5.150
6.4
7.48
8.72
9.72
10.60
11.48
12.2
★25π/4 (challenge corner)

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