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Lines and Angles – Class 6 Mathematics notes, important questions and MCQs

NCERT Class 6 Mathematics, chapter 2. Notes, key terms, important questions with answers and MCQs.

Chapter overview

Points, lines, rays and line segments are the basic ideas of geometry. An angle is formed when two rays meet at a common point.

Basic figures

A line extends endlessly both ways; a ray starts at a point and goes on in one direction; a line segment has two endpoints.
Two lines in a plane either intersect or are parallel.

Angles

An angle is measured in degrees with a protractor.
Types: acute (< 90°), right (90°), obtuse (between 90° and 180°), straight (180°), reflex (between 180° and 360°).
A complete turn is 360°; a half turn is 180°.

Key terms

Ray: part of a line with one endpoint
Vertex: common point where two rays of an angle meet
Right angle: an angle of exactly 90°

Formulas

Complete turn = 360°, straight angle = 180°

Important questions with answers

Classify the angles 45°, 90°, 150° and 210°.2 marks

45° acute, 90° right, 150° obtuse, 210° reflex.

What is the difference between a line, a line segment and a ray?3 marks

A line extends endlessly in both directions; a line segment has two end points and a fixed length; a ray has one end point and extends endlessly in one direction.

Find the angle between the hands of a clock at (i) 6 o'clock, (ii) 2 o'clock, (iii) 9 o'clock, and classify each angle.5 marks

The 12 hour marks divide 360° into 30° parts. (i) 6 o'clock: 6 × 30° = 180°, a straight angle. (ii) 2 o'clock: 2 × 30° = 60°, acute. (iii) 9 o'clock: 9 × 30° = 270° measured one way, or 90° the shorter way; the smaller angle is a right angle.

Quick revision

Acute < 90° < obtuse < 180°.
A line segment has a fixed length.
A full turn is 360°.

Exam tips

Place the protractor's centre on the vertex and the base line on one arm.
The corner of a book or page is a right angle.

Practice MCQs

An angle of 90° is
1. acute
2. right
3. obtuse
4. straight
Show answer
Answer: (b) right. Right angle.
A ray has
1. no endpoint
2. one endpoint
3. two endpoints
4. three endpoints
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Answer: (b) one endpoint. One endpoint.
An angle of 135° is
1. acute
2. right
3. obtuse
4. reflex
Show answer
Answer: (c) obtuse. Between 90° and 180°.
The angle between the hands of a clock at 3 o'clock is
1. 30°
2. 60°
3. 90°
4. 180°
Show answer
Answer: (c) 90°. Quarter turn.
An angle of 135° is
1. acute
2. obtuse
3. right
4. reflex
Show answer
Answer: (b) obtuse. Between 90° and 180°.
The angle between the hands of a clock at 6 o'clock is
1. 180°
2. 90°
3. 360°
4. 0°
Show answer
Answer: (a) 180°. Straight angle.
An angle of 250° is
1. reflex
2. straight
3. obtuse
4. complete
Show answer
Answer: (a) reflex. Between 180° and 360°.
The angle between the hands of a clock at 3 o'clock is
1. 45°
2. 90°
3. 120°
4. 180°
Show answer
Answer: (b) 90°. 3 of 12 equal parts of 360°.

All chapters of Class 6 Mathematics

Written by Kundali IQ from standard, well-established facts to help with revision. This is not an official NCERT publication; always read your textbook too.