Angles — Notes & Practice
Class 5 • Mathematics
1) What is an Angle?
An angle is formed when two rays (or line segments) meet at a common point (called the vertex).
- Sides: The two rays that form the angle.
- Vertex: The common endpoint of the rays.
- Angles are measured in degrees (°).
2) Types of Angles
- Acute angle: Less than 90°
- Right angle: Exactly 90°
- Obtuse angle: Greater than 90° but less than 180°
- Straight angle: Exactly 180°
- Reflex angle: Greater than 180° but less than 360°
- Complete angle: Exactly 360°
3) Properties of Angles
- Angles at a point add up to 360°.
- Angles on a straight line add up to 180°.
- In a triangle, sum of three angles = 180°.
- In a quadrilateral, sum of four angles = 360°.
4) 20 Important Questions & Answers
1) What is an angle?
An angle is formed when two rays meet at a common point called the vertex.
2) What do we call the rays that form an angle?
They are called the sides of the angle.
3) What unit is used to measure an angle?
Angles are measured in degrees (°).
4) What type of angle is 45°?
An acute angle.
5) What type of angle is 90°?
A right angle.
6) What type of angle is 120°?
An obtuse angle.
7) What is a straight angle?
An angle of 180°.
8) What is a reflex angle?
An angle greater than 180° but less than 360°.
9) What is a complete angle?
An angle of 360°.
10) Angles at a point add up to ______.
360°.
11) Angles on a straight line add up to ______.
180°.
12) What is the sum of the angles of a triangle?
180°.
13) What is the sum of the angles of a quadrilateral?
360°.
14) Name an instrument used to measure angles.
A protractor.
15) Which type of angle is less than a right angle?
Acute angle.
16) Which type of angle is greater than a right angle but less than a straight angle?
Obtuse angle.
17) If one angle is 70° and the other is 110°, what type of pair are they?
They form a linear pair (add up to 180°).
18) If an angle measures 0°, what is it called?
A zero angle.
19) How many right angles are there in a straight angle?
Two right angles (2 × 90° = 180°).
20) How many right angles are there in a complete angle?
Four right angles (4 × 90° = 360°).