Free Grade 3 Introduction to Introducing Triangles Common Errors Worksheets
Free Grade 3 worksheets for Introduction to 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
Foundation
30 min
24
Learning objectives
Every objective is checkable, and each one maps to an activity and an assessment.
- RememberIdentify introduction to introducing triangles common errors
Identify introduction to introducing triangles common errors accurately in a familiar context.
Assessed by: Exit ticket of four short items
- UnderstandExplain introduction to introducing triangles common errors
Explain introduction to introducing triangles common errors accurately in a familiar context.
Assessed by: Exit ticket of four short items
- ApplyCalculate introduction to introducing triangles common errors
Calculate introduction to introducing triangles common errors accurately in a familiar context.
Assessed by: Exit ticket of four short items
- AnalyseCompare introduction to introducing triangles common errors
Compare introduction to 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 Introduction to 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 26°. Find the other.[1]
- 2.Two angles on a straight line. One is 145°. Find the other.[1]
- 3.Two angles on a straight line. One is 136°. Find the other.[1]
- 4.Two angles on a straight line. One is 141°. Find the other.[1]
- 5.A triangle has angles 60° and 30°. Find the third angle.[2]
- 6.A triangle has angles 56° and 80°. Find the third angle.[2]
- 7.A triangle has angles 70° and 21°. Find the third angle.[2]
- 8.A triangle has angles 45° and 20°. 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 10-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 9-sided polygon.[3]
Show answers and working
1. 154°
Angles on a straight line add to 180°. 180 − 26 = 154°.
2. 35°
Angles on a straight line add to 180°. 180 − 145 = 35°.
3. 44°
Angles on a straight line add to 180°. 180 − 136 = 44°.
4. 39°
Angles on a straight line add to 180°. 180 − 141 = 39°.
5. 90°
Angles in a triangle add to 180°. 180 − 60 − 30 = 90°.
6. 44°
Angles in a triangle add to 180°. 180 − 56 − 80 = 44°.
7. 89°
Angles in a triangle add to 180°. 180 − 70 − 21 = 89°.
8. 115°
Angles in a triangle add to 180°. 180 − 45 − 20 = 115°.
9. 108°
Sum of interior angles = (5 − 2) × 180 = 540°. Each angle = 540 ÷ 5 = 108°.
10. 144°
Sum of interior angles = (10 − 2) × 180 = 1440°. Each angle = 1440 ÷ 10 = 144°.
11. 128.57°
Sum of interior angles = (7 − 2) × 180 = 900°. Each angle = 900 ÷ 7 = 128.57°.
12. 140°
Sum of interior angles = (9 − 2) × 180 = 1260°. Each angle = 1260 ÷ 9 = 140°.
Worked examples
Two angles on a straight line. One is 105°. Find the other.
- Angles on a straight line add to 180°.
- 180 − 105 = 75°.
- Answer: 75°
A triangle has angles 52° and 47°. Find the third angle.
- Angles in a triangle add to 180°.
- 180 − 52 − 47 = 81°.
- Answer: 81°
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.
Every free resource for Introduction to Introducing Triangles Common Errors
One concept, one ecosystem — all of it free.
Goes deeper
The entities below this one, each with the same complete free resource set.
Sibling concepts
Related concepts
Lateral links, including across subjects.
Next topics
All free formats for this concept
Every kind below is a real page, generated from this entity.
Learn — Meet the idea.
Practice — Build fluency.
Revise — Keep it in memory.
Assess — Prove mastery.
Apply — Use it in context.
Teach — Deliver it to a class.
Frequently asked
- Is this Grade 3 Introduction to Introducing Triangles Common Errors 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 Introducing Triangles Word Problems. 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 Introduction to Introducing Triangles Common Errors?
- Move on to Key Vocabulary of Introducing Triangles Common Errors, Rules and Methods in Introducing Triangles Common Errors, Working with Introducing Triangles Common Errors, Introducing Triangles Common Errors in Examinations, which build directly on this idea.
Related resources
- Free Introduction to Introducing Triangles Common Errors quizzes
- Free Introduction to Introducing Triangles Common Errors flashcards
- Free Introduction to Introducing Triangles Common Errors lessons
- Free Introduction to Introducing Triangles Common Errors lesson plans
- Introduction to Introducing Triangles Common Errors in the knowledge graph
- Free AI Tutor
Stuck on Introduction to Introducing Triangles Common Errors? The AI Tutor already knows this page, its prerequisites and its common mistakes.
Open the free AI Tutor