Free Grade 3 Introducing Angle Bisector Word Problems Lessons
Free Grade 3 lessons for Introducing Angle Bisector Word Problems: 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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25 min
24
Learning objectives
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- UnderstandExplain introducing angle bisector word problems
Explain introducing angle bisector word problems accurately in a familiar context.
Assessed by: Exit ticket of four short items
- ApplyCalculate introducing angle bisector word problems
Calculate introducing angle bisector word problems accurately in a familiar context.
Assessed by: Exit ticket of four short items
- AnalyseCompare introducing angle bisector word problems
Compare introducing angle bisector word problems accurately in a familiar context.
Assessed by: Exit ticket of four short items
- EvaluateJustify introducing angle bisector word problems
Justify introducing angle bisector word problems 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 Introducing Angle Bisector Word Problems 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 107°. Find the other.[1]
- 2.Two angles on a straight line. One is 113°. Find the other.[1]
- 3.Two angles on a straight line. One is 147°. Find the other.[1]
- 4.Two angles on a straight line. One is 99°. Find the other.[1]
- 5.A triangle has angles 50° and 87°. Find the third angle.[2]
- 6.A triangle has angles 65° and 91°. Find the third angle.[2]
- 7.A triangle has angles 75° and 76°. Find the third angle.[2]
- 8.A triangle has angles 76° and 51°. 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 5-sided polygon.[3]
- 11.Find the size of each interior angle of a regular 8-sided polygon.[3]
- 12.Find the size of each interior angle of a regular 6-sided polygon.[3]
Show answers and working
1. 73°
Angles on a straight line add to 180°. 180 − 107 = 73°.
2. 67°
Angles on a straight line add to 180°. 180 − 113 = 67°.
3. 33°
Angles on a straight line add to 180°. 180 − 147 = 33°.
4. 81°
Angles on a straight line add to 180°. 180 − 99 = 81°.
5. 43°
Angles in a triangle add to 180°. 180 − 50 − 87 = 43°.
6. 24°
Angles in a triangle add to 180°. 180 − 65 − 91 = 24°.
7. 29°
Angles in a triangle add to 180°. 180 − 75 − 76 = 29°.
8. 53°
Angles in a triangle add to 180°. 180 − 76 − 51 = 53°.
9. 128.57°
Sum of interior angles = (7 − 2) × 180 = 900°. Each angle = 900 ÷ 7 = 128.57°.
10. 108°
Sum of interior angles = (5 − 2) × 180 = 540°. Each angle = 540 ÷ 5 = 108°.
11. 135°
Sum of interior angles = (8 − 2) × 180 = 1080°. Each angle = 1080 ÷ 8 = 135°.
12. 120°
Sum of interior angles = (6 − 2) × 180 = 720°. Each angle = 720 ÷ 6 = 120°.
Worked examples
Two angles on a straight line. One is 23°. Find the other.
- Angles on a straight line add to 180°.
- 180 − 23 = 157°.
- Answer: 157°
A triangle has angles 46° and 48°. Find the third angle.
- Angles in a triangle add to 180°.
- 180 − 46 − 48 = 86°.
- Answer: 86°
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
- Is this Grade 3 Introducing Angle Bisector Word Problems 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 Introducing Angle Bisector Techniques, Introducing Angle Bisector Essentials, Perpendicular Bisector. 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 Introducing Angle Bisector Word Problems?
- Move on to Introducing Angle Bisector Common Errors, Working with Angle Bisector, Angle Bisector in Context, which build directly on this idea.
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