Angles 60°, 60°, and 60°
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Equiangular and acute
Free printable worksheet
Triangle Properties Worksheet
Twenty problems involving angle sums, classifications, and the triangle inequality.
Middle School MathGrades 6-83 pagesAnswer key included
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What this worksheet includes
- Twenty problems involving angle sums, classifications, and the triangle inequality.
- 3-page printable PDF with a complete answer key
- Designed for Grades 6-8 middle school math practice
- Available as an immediate free download with no email required
How to use it
Use this triangle properties worksheet for guided practice, independent review, homework, tutoring sessions, or a quick skills check. The spacious layout is designed to leave room for students to show their work rather than guess from crowded answer choices.
After students finish, compare their reasoning with the included answer key. When an answer is incorrect, have the student locate the first step where their work changed direction before trying the problem again.
Who this practice is for
This resource is designed for grades 6-8 students working on middle school math. Teachers, tutors, homeschool families, and parents can preview the first page before deciding whether the level and spacing fit the student.
Looking for a broader sequence? Browse all Middle School Math worksheets.
Topic guide
How to approach triangle properties
Every triangle has interior angles totaling 180°. Triangles can be classified by side lengths or angle measures, and their side lengths must satisfy the triangle inequality.
Use congruence markings and stated measurements rather than visual estimates. An isosceles triangle's equal sides lie opposite equal base angles.
Learning objectives
- Find missing triangle angles
- Classify triangles
- Apply triangle inequality and isosceles properties
Skills to review first
- Angle measurement
- Solving simple equations
- Comparing side lengths
Worked example
Follow the reasoning step by step
A triangle has angles 48° and 67°. Find the third angle.
- Triangle angles total 180°.
- Add known angles: 48 + 67 = 115.
- Subtract 115 from 180.
- Check that all three measures total 180°.
Solution: 65°.
Try before downloading
Three sample problems
Work each problem, then open the answer to check your result.
Sides 5, 5, and 8
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Isosceles triangle
Can 3, 4, and 8 form a triangle?
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No; 3 + 4 is not greater than 8.
Error check
Common mistakes to watch for
- Using 360° for a triangle's angle sum
- Matching equal angles with adjacent instead of opposite sides
- Checking only one triangle-inequality pair