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Grade 10 similar triangles worksheets

HSG-SRT.B.5 Measurement and geometry

Printable similar triangles worksheets for grade 10, aligned to Common Core standard HSG-SRT.B.5. Scale every side the same way.

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Sample problems

  1. Two triangles are similar. The first has sides 3, 5, 7 (in the same units). The shortest side of the second triangle is 12. What is the second triangle's longest side? 28
  2. Two triangles are similar. The first has sides 3, 5, 7 (in the same units). The shortest side of the second triangle is 15. What is the second triangle's longest side? 35
  3. Two triangles are similar. The first has sides 3, 4, 5 (in the same units). The shortest side of the second triangle is 15. What is the second triangle's longest side? 25
  4. Two triangles are similar. The first has sides 3, 5, 7 (in the same units). The shortest side of the second triangle is 9. What is the second triangle's longest side? 21
  5. Two triangles are similar. The first has sides 3, 4, 5 (in the same units). The shortest side of the second triangle is 12. What is the second triangle's longest side? 20
  6. Two triangles are similar. The first has sides 2, 3, 4 (in the same units). The shortest side of the second triangle is 8. What is the second triangle's longest side? 16
  7. Two triangles are similar. The first has sides 5, 6, 7 (in the same units). The shortest side of the second triangle is 15. What is the second triangle's longest side? 21
  8. Two triangles are similar. The first has sides 4, 5, 6 (in the same units). The shortest side of the second triangle is 20. What is the second triangle's longest side? 30

These eight are one sample at medium difficulty — the generator makes a different set every time.

A worked example

Two triangles are similar. The first has sides 3, 5, 7 (in the same units). The shortest side of the second triangle is 12. What is the second triangle's longest side? 28

  1. Find the scale factor from the shortest sides: 12 ÷ 3 = 4
  2. Similar triangles scale every side the same way, so longest side: 7 × 4 = 28

Every problem on the answer key can show its steps like this — turn on “Show steps” before downloading.

About these worksheets

Each problem states its own measurements, so the reasoning is the same but the arithmetic is new every time. Every sheet is generated fresh, so you can print a new one on the same skill as often as you need — different numbers, same difficulty.

Pick how many problems you want and whether they should be easy, medium or hard, then download a PDF with a matching answer key. The key can show the worked steps for every problem, which is what a parent needs to see where a wrong answer went wrong.

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