Types of Angles for Class 6
Introduction
Angles are an important part of geometry. We see angles everywhere around us—in clocks, doors, books, roads, and buildings. An angle is formed when two rays meet at a common endpoint called the vertex.
Understanding the different types of angles helps students solve geometry problems and understand shapes better.
What is an Angle?
An angle is the space between two rays that start from the same point.
Parts of an Angle
- Vertex: The common endpoint where two rays meet.
- Arms: The two rays that form the angle.
Example:
A
\
\
O------B
Here, O is the vertex and OA and OB are the arms.
Types of Angles
Angles are classified according to their measurements.
1. Acute Angle
An acute angle is an angle that measures more than 0° but less than 90°.
Examples: 20°, 35°, 45°, 75°
Image
/
/
/
/
O---------
45°
Real-Life Examples
- Slice of pizza
- Open scissors
- Clock hands at 1 o’clock
2. Right Angle
A right angle measures exactly 90°.
Example: 90°
Image
|
|
|
O---------
90°
Real-Life Examples
- Corner of a book
- Window frame
- Square tile
3. Obtuse Angle
An obtuse angle measures more than 90° but less than 180°.
Examples: 100°, 120°, 150°
Image
\
\
\
O---------
120°
Real-Life Examples
- A widely opened door
- Clock hands at certain times
- Some road sign shapes
4. Straight Angle
A straight angle measures exactly 180°.
Image
<---------O--------->
180°
Real-Life Examples
- A straight road
- A ruler
- A stretched rope
5. Reflex Angle
A reflex angle measures more than 180° but less than 360°.
Examples: 200°, 250°, 300°
Image
/
/
/
O---------
\________
240°
Real-Life Examples
- Rotation of a fan blade
- Turning a steering wheel more than half a turn
6. Complete Angle
A complete angle measures exactly 360°.
Image
↑
↗ ↖
← O →
↘ ↙
↓
360°
Real-Life Examples
- One full rotation of a wheel
- One complete turn of a spinning top
Summary Table
| Type of Angle | Measurement |
|---|---|
| Acute Angle | Greater than 0° and less than 90° |
| Right Angle | Exactly 90° |
| Obtuse Angle | Greater than 90° and less than 180° |
| Straight Angle | Exactly 180° |
| Reflex Angle | Greater than 180° and less than 360° |
| Complete Angle | Exactly 360° |
Everyday Uses of Angles
Angles are used in:
- Architecture and construction
- Drawing and design
- Road planning
- Sports
- Navigation
- Engineering
Practice Questions
Multiple Choice Questions
- Which angle measures exactly 90°?
- a) Acute angle
- b) Right angle
- c) Obtuse angle
- d) Reflex angle
- An angle of 45° is:
- a) Acute angle
- b) Right angle
- c) Straight angle
- d) Reflex angle
- Which angle measures 180°?
- a) Acute angle
- b) Obtuse angle
- c) Straight angle
- d) Complete angle
- An angle of 250° is:
- a) Acute angle
- b) Obtuse angle
- c) Straight angle
- d) Reflex angle
Fill in the Blanks
- A right angle measures ________.
- An acute angle is less than ________.
- A straight angle measures ________.
- A complete angle measures ________.
Answers
MCQs: 1-b, 2-a, 3-c, 4-d
Fill in the blanks:
- 90°
- 90°
- 180°
- 360°