Triangle Sum Theorem - Worksheet 6 - 10th Grade

Medium

Apply the triangle angle sum theorem (Medium)

24 problems · 15-20 minutes · Skills: triangles, angles, geometry

About This Worksheet

This medium-level worksheet contains 24 problems designed for 10th Grade students practicing triangle sum theorem. Medium worksheets introduce larger numbers and varied question formats to deepen understanding and build fluency.

The Triangle Angle Sum Theorem is one of the most frequently used facts in all of geometry. It connects directly to parallel line theory and is prerequisite knowledge for congruence proofs, trigonometry, and polygon angle calculations.

  • State and apply the Triangle Angle Sum Theorem (angles sum to 180 degrees)
  • Find missing angle measures in triangles using the theorem
  • Apply the Exterior Angle Theorem to solve for unknown angles
  • Classify triangles as acute, right, or obtuse using their angle measures
  • Write algebraic equations from angle sum conditions and solve for unknown variables

How to Solve: Worked Example

Example Problem: Solve the first problem on the worksheet.
Solution Steps:
  1. Read the problem carefully.
  2. Identify what is being asked.
  3. Use what you know to find the answer.
  4. Check your work.
Answer: See the answer key below
Tip: Take your time and read each problem carefully before answering!
1
7 + 4 =
2
2 + 6 =
3
10 + 4 =
4
10 + 7 =
5
1 + 5 =
6
6 + 5 =
7
5 + 4 =
8
7 + 3 =
9
9 + 5 =
10
9 + 4 =
11
3 + 2 =
12
5 + 5 =
13
5 + 5 =
14
9 + 7 =
15
10 + 8 =
16
7 + 7 =
17
9 + 10 =
18
6 + 3 =
19
9 + 2 =
20
8 + 4 =
21
6 + 9 =
22
3 + 2 =
23
4 + 1 =
24
9 + 4 =

Answer Key

1. 112. 83. 144. 175. 66. 117. 98. 109. 1410. 1311. 512. 1013. 1014. 1615. 1816. 1417. 1918. 919. 1120. 1221. 1522. 523. 524. 13

Frequently Asked Questions

How do I download this triangle sum theorem - worksheet 6 worksheet?

Click the "Download PDF / Print" button at the top of the worksheet. You can save it as a PDF or print it directly. The answer key will be on a separate page.

How do I find worksheets at different difficulty levels?

Each subtopic has 10 worksheets: Worksheets 1-3 are Easy, 4-7 are Medium, and 8-10 are Hard. Start with Easy worksheets to build confidence, then progress to harder ones.

What skills does this triangles worksheet cover?

This worksheet focuses on triangles, angles, geometry. It is designed for 10th Grade students and provides structured practice through varied problem types with a worked example to guide students before they begin.

Can I use this worksheet in my classroom?

Yes. All worksheets on K12Worksheets are free for classroom use. You can print copies for your entire class. With 10 worksheets per subtopic at three difficulty levels, you have plenty of options for differentiated instruction and individualized practice.

How many problems are on this worksheet?

This worksheet contains 24 problems. It typically takes 15-20 minutes to complete. An answer key with all solutions is included so parents and teachers can check work quickly.