Free Grade 3 Triangles in Context Worksheets
Free Grade 3 worksheets for Triangles in Context: 12 real questions with a full answer key and worked solutions. Angles on a straight line add to 180°, around a point to 360°, and inside a triangle to 180°. A polygon with n sides has interior angles adding to (n − 2) × 180°.
Free
Higher
20 min
24
Learning objectives
Every objective is checkable, and each one maps to an activity and an assessment.
- RememberIdentify triangles in context
Identify triangles in context accurately in a familiar context.
Assessed by: Exit ticket of four short items
- UnderstandExplain triangles in context
Explain triangles in context accurately in a familiar context.
Assessed by: Exit ticket of four short items
- ApplyCalculate triangles in context
Calculate triangles in context accurately in a familiar context.
Assessed by: Exit ticket of four short items
- AnalyseCompare triangles in context
Compare triangles in context accurately in a familiar context.
Assessed by: Exit ticket of four short items
Prerequisites
Close these gaps first — each has its own free lesson, worksheet and quiz.
How Triangles in Context works
Angles on a straight line add to 180°, around a point to 360°, and inside a triangle to 180°. A polygon with n sides has interior angles adding to (n − 2) × 180°.
12 practice questions
Easy to hard, 24 marks in total. Try them first, then open the answers.
- 1.Two angles on a straight line. One is 79°. Find the other.[1]
- 2.Two angles on a straight line. One is 159°. Find the other.[1]
- 3.Two angles on a straight line. One is 156°. Find the other.[1]
- 4.Two angles on a straight line. One is 63°. Find the other.[1]
- 5.A triangle has angles 39° and 23°. Find the third angle.[2]
- 6.A triangle has angles 64° and 70°. Find the third angle.[2]
- 7.A triangle has angles 37° and 29°. Find the third angle.[2]
- 8.A triangle has angles 33° and 104°. Find the third angle.[2]
- 9.Find the size of each interior angle of a regular 6-sided polygon.[3]
- 10.Find the size of each interior angle of a regular 5-sided polygon.[3]
- 11.Find the size of each interior angle of a regular 7-sided polygon.[3]
- 12.Find the size of each interior angle of a regular 8-sided polygon.[3]
Show answers and working
1. 101°
Angles on a straight line add to 180°. 180 − 79 = 101°.
2. 21°
Angles on a straight line add to 180°. 180 − 159 = 21°.
3. 24°
Angles on a straight line add to 180°. 180 − 156 = 24°.
4. 117°
Angles on a straight line add to 180°. 180 − 63 = 117°.
5. 118°
Angles in a triangle add to 180°. 180 − 39 − 23 = 118°.
6. 46°
Angles in a triangle add to 180°. 180 − 64 − 70 = 46°.
7. 114°
Angles in a triangle add to 180°. 180 − 37 − 29 = 114°.
8. 43°
Angles in a triangle add to 180°. 180 − 33 − 104 = 43°.
9. 120°
Sum of interior angles = (6 − 2) × 180 = 720°. Each angle = 720 ÷ 6 = 120°.
10. 108°
Sum of interior angles = (5 − 2) × 180 = 540°. Each angle = 540 ÷ 5 = 108°.
11. 128.57°
Sum of interior angles = (7 − 2) × 180 = 900°. Each angle = 900 ÷ 7 = 128.57°.
12. 135°
Sum of interior angles = (8 − 2) × 180 = 1080°. Each angle = 1080 ÷ 8 = 135°.
Worked examples
Two angles on a straight line. One is 111°. Find the other.
- Angles on a straight line add to 180°.
- 180 − 111 = 69°.
- Answer: 69°
A triangle has angles 40° and 35°. Find the third angle.
- Angles in a triangle add to 180°.
- 180 − 40 − 35 = 105°.
- Answer: 105°
Find the size of each interior angle of a regular 9-sided polygon.
- Sum of interior angles = (9 − 2) × 180 = 1260°.
- Each angle = 1260 ÷ 9 = 140°.
- Answer: 140°
Interactive practice
Free, no account required — answer on screen or print it.
Common mistakes
What learners typically get wrong, and how to fix it.
Reads the wrong scale on a protractor.
Correction: Start from the 0 on the arm you are measuring from.
Uses 360° for a triangle.
Correction: Triangle = 180°, quadrilateral = 360°.
Teacher tips
- · Estimate the angle type before measuring.
Parent tips
- · Spot right angles around the house.
Real-life applications
- · Ramps, clock hands, building and design.
Assessment objectives
How mastery is evidenced, and which standards it maps to.
Every free resource for Triangles in Context
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Learn — Meet the idea.
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Frequently asked
- Is this Grade 3 Triangles in Context worksheet really free?
- Yes. Every worksheets on FreeMathWorksheet is free to use, print and share — no account, no paywall and no watermark.
- What should a learner already know before this?
- Start with Working with Triangles, Introducing Triangles, Angles. Each one has its own free lesson, worksheet and quiz.
- How is the worksheet sequenced?
- Recognition first, then understanding, application, reasoning and finally mastery — the same ladder used across every free resource on the platform.
- What comes next after Triangles in Context?
- Move on to Quadrilaterals, Circles, Polygons, Symmetry, which build directly on this idea.
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