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JAC • Class 6 • Mathematics • Ch 11

Estimated Time: 45 Mins

Study Progress: In Progress

Angles

Identify an angle’s arms and vertex, measure it with a protractor and classify it by size.

View All Chapters JCERT Hindi Textbook

Overview Core Concepts Solved Examples Common Traps Summary Self Check Take MCQ Test

Why This Chapter Matters

Identify an angle’s arms and vertex, measure it with a protractor and classify it by size.

Before You Begin (Prerequisites)

Familiarity with simple shapes and measurement

What You Will Learn (Core Objectives)

Identify an angle’s arms and vertex, measure it with a protractor and classify it by size.

Chapter Roadmap & Progression

1 Syllabus and book alignment

2 Concept 1

3 Concept 2

4 Concept 3

Complete Concept Guide (100% Curriculum Coverage)

Syllabus and book alignment

JCERT 2026–27: Regular schools (Non-SOE) — Chapter 11 · Angles. Syllabus pages 186–200. These notes follow this topic. Official syllabus. Official JCERT Hindi textbook. Some source PDFs are damaged. The supplementary reference uses different chapter numbering.

Concept 1

Two rays with a common endpoint form an angle. In ∠ABC, B is the vertex and BA and BC are its arms. The middle letter always names the vertex. Points between the arms in the smaller angular region lie in its interior; points in the other region lie in its exterior.

Concept 2

An acute angle is greater than 0° and less than 90°; a right angle is 90°; an obtuse angle is greater than 90° and less than 180°. A straight angle is 180°, a reflex angle is greater than 180° and less than 360°, and a complete turn is 360°.

Concept 3

Place the protractor’s centre at the vertex and its baseline along one arm. Read the scale that starts at 0° on that arm. Longer arms do not change an angle’s measure. Use 45°, 90° and 180° as benchmarks to estimate angles.

Conceptual Solved Examples & Case Studies

Example 1

Classify 35°, 90°, 125° and 180°.

Step-by-Step Solution:

35° is acute; 90° is right; 125° is obtuse; 180° is straight.

Common Misconceptions & Examiner Traps

Common Misconception

Common misconception

Scientific Reality & Correction

Use the correct protractor scale; do not confuse 60° with 120°.

Chapter Summary & 10 Key Takeaways

Takeaway 1

Takeaway 2

Takeaway 3

Check Your Understanding (Diagnostic Practice Questions)

Diagnostic questions testing core conceptual clarity. Answers are hidden initially — solve each problem first, then click to reveal the step-by-step verified solution.

How many degrees are in three quarters of a complete turn?

Reveal Answer & Explanation

Answer: (3 ÷ 4) × 360° = 270°, a reflex angle.
Use the definition above.

Chapter practice

CBT tests for this chapter are not published yet. Solve the self-check questions above and compare your answers.

All Class 6 Mathematics Chapters

Ch 1: Knowing Our Numbers Ch 2: Whole Numbers Ch 3: Integers Ch 4: Playing with Numbers Ch 5: Fractions Ch 6: Decimals Ch 7: Ratio and Proportion Ch 8: Algebra Ch 9: Line, Line Segment and Ray Ch 10: Pairs of Lines Ch 11: Angles Ch 12: Polygons Ch 13: Circle Ch 14: Three-Dimensional Shapes Ch 15: Symmetry Ch 16: Practical Geometry Ch 17: Perimeter and Area Ch 18: Data Handling

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