Free Grade 3 Working with Introducing Triangles Common Errors Quizzes
Free Grade 3 quizzes for Working with Introducing Triangles Common Errors: 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
25 min
24
Learning objectives
Every objective is checkable, and each one maps to an activity and an assessment.
- RememberIdentify working with introducing triangles common errors
Identify working with introducing triangles common errors accurately in a familiar context.
Assessed by: Exit ticket of four short items
- UnderstandExplain working with introducing triangles common errors
Explain working with introducing triangles common errors accurately in a familiar context.
Assessed by: Exit ticket of four short items
- ApplyCalculate working with introducing triangles common errors
Calculate working with introducing triangles common errors accurately in a familiar context.
Assessed by: Exit ticket of four short items
- AnalyseCompare working with introducing triangles common errors
Compare working with introducing triangles common errors 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 Working with Introducing Triangles Common Errors 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 93°. Find the other.[1]
- 2.Two angles on a straight line. One is 31°. Find the other.[1]
- 3.Two angles on a straight line. One is 38°. Find the other.[1]
- 4.Two angles on a straight line. One is 89°. Find the other.[1]
- 5.A triangle has angles 53° and 45°. Find the third angle.[2]
- 6.A triangle has angles 81° and 67°. Find the third angle.[2]
- 7.A triangle has angles 86° and 28°. Find the third angle.[2]
- 8.A triangle has angles 56° and 103°. Find the third angle.[2]
- 9.Find the size of each interior angle of a regular 9-sided polygon.[3]
- 10.Find the size of each interior angle of a regular 7-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 8-sided polygon.[3]
Show answers and working
1. 87°
Angles on a straight line add to 180°. 180 − 93 = 87°.
2. 149°
Angles on a straight line add to 180°. 180 − 31 = 149°.
3. 142°
Angles on a straight line add to 180°. 180 − 38 = 142°.
4. 91°
Angles on a straight line add to 180°. 180 − 89 = 91°.
5. 82°
Angles in a triangle add to 180°. 180 − 53 − 45 = 82°.
6. 32°
Angles in a triangle add to 180°. 180 − 81 − 67 = 32°.
7. 66°
Angles in a triangle add to 180°. 180 − 86 − 28 = 66°.
8. 21°
Angles in a triangle add to 180°. 180 − 56 − 103 = 21°.
9. 140°
Sum of interior angles = (9 − 2) × 180 = 1260°. Each angle = 1260 ÷ 9 = 140°.
10. 128.57°
Sum of interior angles = (7 − 2) × 180 = 900°. Each angle = 900 ÷ 7 = 128.57°.
11. 120°
Sum of interior angles = (6 − 2) × 180 = 720°. Each angle = 720 ÷ 6 = 120°.
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 20°. Find the other.
- Angles on a straight line add to 180°.
- 180 − 20 = 160°.
- Answer: 160°
A triangle has angles 49° and 80°. Find the third angle.
- Angles in a triangle add to 180°.
- 180 − 49 − 80 = 51°.
- Answer: 51°
Find the size of each interior angle of a regular 10-sided polygon.
- Sum of interior angles = (10 − 2) × 180 = 1440°.
- Each angle = 1440 ÷ 10 = 144°.
- Answer: 144°
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
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Frequently asked
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- What should a learner already know before this?
- Start with Rules and Methods in Introducing Triangles Common Errors, Key Vocabulary of Introducing Triangles Common Errors, Introducing Triangles Word Problems. Each one has its own free lesson, worksheet and quiz.
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- Recognition first, then understanding, application, reasoning and finally mastery — the same ladder used across every free resource on the platform.
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- Move on to Introducing Triangles Common Errors in Examinations, Introducing Triangles Essentials, Introducing Triangles Techniques, Introducing Triangles Word Problems, which build directly on this idea.
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