Free Grade 3 Vertically Opposite Angles in Context Lessons
Free Grade 3 lessons for Vertically Opposite Angles 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
Core
35 min
24
Learning objectives
Every objective is checkable, and each one maps to an activity and an assessment.
- UnderstandExplain vertically opposite angles in context
Explain vertically opposite angles in context accurately in a familiar context.
Assessed by: Exit ticket of four short items
- ApplyCalculate vertically opposite angles in context
Calculate vertically opposite angles in context accurately in a familiar context.
Assessed by: Exit ticket of four short items
- AnalyseCompare vertically opposite angles in context
Compare vertically opposite angles in context accurately in a familiar context.
Assessed by: Exit ticket of four short items
- EvaluateJustify vertically opposite angles in context
Justify vertically opposite angles 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 Vertically Opposite Angles 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 31°. Find the other.[1]
- 2.Two angles on a straight line. One is 110°. Find the other.[1]
- 3.Two angles on a straight line. One is 106°. Find the other.[1]
- 4.Two angles on a straight line. One is 133°. Find the other.[1]
- 5.A triangle has angles 60° and 88°. Find the third angle.[2]
- 6.A triangle has angles 22° and 36°. Find the third angle.[2]
- 7.A triangle has angles 37° and 48°. Find the third angle.[2]
- 8.A triangle has angles 29° and 122°. Find the third angle.[2]
- 9.Find the size of each interior angle of a regular 5-sided polygon.[3]
- 10.Find the size of each interior angle of a regular 8-sided polygon.[3]
- 11.Find the size of each interior angle of a regular 6-sided polygon.[3]
- 12.Find the size of each interior angle of a regular 10-sided polygon.[3]
Show answers and working
1. 149°
Angles on a straight line add to 180°. 180 − 31 = 149°.
2. 70°
Angles on a straight line add to 180°. 180 − 110 = 70°.
3. 74°
Angles on a straight line add to 180°. 180 − 106 = 74°.
4. 47°
Angles on a straight line add to 180°. 180 − 133 = 47°.
5. 32°
Angles in a triangle add to 180°. 180 − 60 − 88 = 32°.
6. 122°
Angles in a triangle add to 180°. 180 − 22 − 36 = 122°.
7. 95°
Angles in a triangle add to 180°. 180 − 37 − 48 = 95°.
8. 29°
Angles in a triangle add to 180°. 180 − 29 − 122 = 29°.
9. 108°
Sum of interior angles = (5 − 2) × 180 = 540°. Each angle = 540 ÷ 5 = 108°.
10. 135°
Sum of interior angles = (8 − 2) × 180 = 1080°. Each angle = 1080 ÷ 8 = 135°.
11. 120°
Sum of interior angles = (6 − 2) × 180 = 720°. Each angle = 720 ÷ 6 = 120°.
12. 144°
Sum of interior angles = (10 − 2) × 180 = 1440°. Each angle = 1440 ÷ 10 = 144°.
Worked examples
Two angles on a straight line. One is 142°. Find the other.
- Angles on a straight line add to 180°.
- 180 − 142 = 38°.
- Answer: 38°
A triangle has angles 54° and 78°. Find the third angle.
- Angles in a triangle add to 180°.
- 180 − 54 − 78 = 48°.
- Answer: 48°
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.
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Frequently asked
- Is this Grade 3 Vertically Opposite Angles in Context lesson really free?
- Yes. Every lessons 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 Vertically Opposite Angles, Introducing Vertically Opposite Angles, Angles Around a Point. Each one has its own free lesson, worksheet and quiz.
- How is the lesson 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 Vertically Opposite Angles in Context?
- Move on to Angles on a Straight Line, Angles Around a Point, Angles in Parallel Lines, Angles in Polygons, which build directly on this idea.
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