Free Grade 3 Angles in Parallel Lines Flashcards
Free Grade 3 flashcards for Angles in Parallel Lines: 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°.
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20 min
24
Learning objectives
Every objective is checkable, and each one maps to an activity and an assessment.
- RememberIdentify angles in parallel lines
Identify angles in parallel lines accurately in a familiar context.
Assessed by: Exit ticket of four short items
- UnderstandExplain angles in parallel lines
Explain angles in parallel lines accurately in a familiar context.
Assessed by: Exit ticket of four short items
- ApplyCalculate angles in parallel lines
Calculate angles in parallel lines accurately in a familiar context.
Assessed by: Exit ticket of four short items
- AnalyseCompare angles in parallel lines
Compare angles in parallel lines 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 Angles in Parallel Lines 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 135°. Find the other.[1]
- 2.Two angles on a straight line. One is 81°. Find the other.[1]
- 3.Two angles on a straight line. One is 49°. Find the other.[1]
- 4.Two angles on a straight line. One is 144°. Find the other.[1]
- 5.A triangle has angles 20° and 30°. Find the third angle.[2]
- 6.A triangle has angles 40° and 64°. Find the third angle.[2]
- 7.A triangle has angles 29° and 49°. Find the third angle.[2]
- 8.A triangle has angles 60° and 75°. Find the third angle.[2]
- 9.Find the size of each interior angle of a regular 7-sided polygon.[3]
- 10.Find the size of each interior angle of a regular 6-sided polygon.[3]
- 11.Find the size of each interior angle of a regular 9-sided polygon.[3]
- 12.Find the size of each interior angle of a regular 10-sided polygon.[3]
Show answers and working
1. 45°
Angles on a straight line add to 180°. 180 − 135 = 45°.
2. 99°
Angles on a straight line add to 180°. 180 − 81 = 99°.
3. 131°
Angles on a straight line add to 180°. 180 − 49 = 131°.
4. 36°
Angles on a straight line add to 180°. 180 − 144 = 36°.
5. 130°
Angles in a triangle add to 180°. 180 − 20 − 30 = 130°.
6. 76°
Angles in a triangle add to 180°. 180 − 40 − 64 = 76°.
7. 102°
Angles in a triangle add to 180°. 180 − 29 − 49 = 102°.
8. 45°
Angles in a triangle add to 180°. 180 − 60 − 75 = 45°.
9. 128.57°
Sum of interior angles = (7 − 2) × 180 = 900°. Each angle = 900 ÷ 7 = 128.57°.
10. 120°
Sum of interior angles = (6 − 2) × 180 = 720°. Each angle = 720 ÷ 6 = 120°.
11. 140°
Sum of interior angles = (9 − 2) × 180 = 1260°. Each angle = 1260 ÷ 9 = 140°.
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 85°. Find the other.
- Angles on a straight line add to 180°.
- 180 − 85 = 95°.
- Answer: 95°
A triangle has angles 76° and 53°. Find the third angle.
- Angles in a triangle add to 180°.
- 180 − 76 − 53 = 51°.
- Answer: 51°
Find the size of each interior angle of a regular 8-sided polygon.
- Sum of interior angles = (8 − 2) × 180 = 1080°.
- Each angle = 1080 ÷ 8 = 135°.
- Answer: 135°
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 Angles in Parallel Lines flashcards really free?
- Yes. Every flashcards 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 Vertically Opposite Angles, Angles Around a Point, Algebra. Each one has its own free lesson, worksheet and quiz.
- How is the flashcards 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 Angles in Parallel Lines?
- Move on to Angles in Polygons, 2D Shapes, Perimeter and Area, 3D Shapes, which build directly on this idea.
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