Types of Angles

Topics

Number System(Consolidating the Sense of Numberness)
- Comparing Numbers
- To Form The Smallest and The Greatest Numbers Using Given Digits
- Operations on Larger Numbers
Number System
Estimation
- Basic Concept of Estimation and Approximation of Numbers
- Rounding off a Number
- Estimation in Basic Operations
Ratio and Proportion
Algebra
Numbers in India and International System (With Comparison)
- Concept of Unit, Number, Numeral and Numeration
- Hindu-Arabic (Indian) System of Numeration
- International System of Numeration
- Indian vs. International Place Value System
Geometry
Place Value
- Concept of Place Value
- Largest and Smallest Numbers
Mensuration
Natural Numbers and Whole Numbers (Including Patterns)
- Natural Numbers
- Whole Numbers
- Successor and Predecessor of Whole Number
- Properties of Whole Numbers
- Mathematical Patterns
- Patterns in Whole/Natural Numbers
- Magic Square
- Matchstick Pattern
Data Handling
Negative Numbers and Integers
- Concept of Negative Numbers
- Integers
- Ordering of Integers
- Addition of Integers
- Subtraction of Integers
- Integers
Number Line
- Number Line
- Representation of Natural numbers, Whole Numbers and Integers On Number Line
- Comparing Numbers
- Addition and Subtraction on a Number Line
HCF and LCM
- Factors and Common Factors
- Prime and Composite Numbers
- Eratosthenes’ Method of Finding Prime Numbers
- Prime Factorisation
- Highest Common Factor (HCF)
- Methods of Finding HCF
- Multiples and Common Multiples
- Lowest Common Multiple
- Methods of Finding LCM
Playing with Numbers
- Simplification of Brackets
- Finding Factors Using Rectangular Arrangements and Division
- Factors and Common Factors
- Multiples and Common Multiples
- Concept of Even and Odd Number
- Tests for Divisibility of Numbers
- Divisibility by 2
- Divisibility by 4
- Divisibility by 8
- Divisibility by 3
- Divisibility by 6
- Divisibility by 9
- Divisibility by 5
- Divisibility by 11
Sets
- Concept of Sets
- Representation of a Set
- Types of Sets
- Cardinality of a Set
Ratio
- Quantitative Comparison Using Basic Operations
- Ratio
- Simplifying Ratios
- Problems based on Ratio
- All About Ratios: Dividing, Comparing, and Modifying Quantities
Proportion (Including Word Problems)
- Proportion
- Concept of Continued Proportion
Unitary Method
- Unitary Method
- Types of Variation
Fractions
- Concept of Fraction
- Types of Fractions
- Concept of Proper and Improper Fractions
- Concept of Mixed Fractions
- Like and Unlike Fraction
- Concept of Equivalent Fractions
- Conversion between Improper and Mixed fraction
- Conversion between Unlike and Like Fractions
- Simplest Form of a Fractions
- Comparing Fractions
- Addition of Fraction
- Subtraction of Fraction
- Multiplication of Fraction
- Division of Fractions
- Using Operator 'Of' with Multiplication and Division
- BODMAS Rule
- Problems Based on Fraction
Decimal Fractions
- Like and Unlike Decimal Numbers
- The Decimal Number System
- Conversion between Decimal Fraction and Common Fraction
- Addition of Decimal Fraction
- Subtraction of Decimal Numbers
- Multiplication of Decimal Numbers
- Division of Decimal Numbers
- Application of Decimals in Real Life
- Word Problems based on Decimals
Percent (Percentage)
- Basic Concept of Percentage
- Conversion between Percentage and Fraction or Decimal
- Expressing Quantities as Percentages
- Increase or Decrease in Percent
- Percentage Problems Related to Environment
Idea of Speed, Distance and Time
- Speed, Distance and Time
- Uniform Speed, Variable Speed, and Conversions
Fundamental Concepts
- Introduction to Algebra
- Constants and Variables in Mathematics
- Classification of Terms in Algebra
- Algebraic Expressions
- Factors and Common Factors
- Powers and Exponents
- Basic Concept of Polynomial and its Degree
Fundamental Operations (Related to Algebraic Expressions)
- Addition of Like and Unlike Terms
- Subtraction of Like and Unlike Terms
- Addition of Polynomials
- Subtraction of Polynomials
- Multiplication of Algebraic Expressions
- Division of Algebraic Expressions
Substitution (Including Use of Brackets as Grouping Symbols)
- Basic Concept of Substitution
- Brackets in Mathematics
Framing Algebraic Expressions (Including Evaluation)
- Algebraic Expressions
- Evaluation of Algebraic Expressions
Simple (Linear) Equations (Including Word Problems)
- Concept of Linear Equations
- Rules for Solving a Linear Equation
- Methods of Solving Linear Equations
- Word Problems on Linear Equations
Fundamental Concepts
- Fundamentals of Geometrical Concepts
- Concept of Points
- Concept of Lines
- Rays
- Line Segments
- Mathematical Concept of Surface
- Planes
- Parallel Lines
- Intersecting Lines
- Concept for Open and Closed Figures
- Plane Closed Figures
- The Perpendicular
- The Perpendicular Bisector
Angles (With Their Types)
- Concept of Angle
- Angle and Its Formation
- Measuring Angles
- Types of Angles
- Concept of Pairs of Angles
- The Sum of the Angles Around a Point is Always 360°
Properties of Angles and Lines (Including Parallel Lines)
- Properties of Adjacent and Vertically Opposite Angles
- Parallel Lines
- Concept of Transversal Lines
- Construction of an Angle
- Drawing a Perpendicular to a Line
Triangles (Including Types, Properties and Constructions)
- Basic Concepts of Triangles
- Exterior Angle of a Triangle and Its Property
- Classification of Triangles based on Angles
- Classification of Triangles based on Sides
- Altitudes of a Triangle
- Median of a Triangle
- Construction of Triangles
Quadrilateral
- Quadrilaterals
- Angle sum Property of Quadrilateral
- Types of Quadrilaterals
Polygons
- Basic Concept of Polygons
- Sum of Interior Angles of a Polygon
- Sum of Exterior Angles of a Polygon
- Basic Concept of Regular Polygon
The Circle
- Basic Concept of Circle
- Secant and Tangent
- Arc of the Circle
- Sector of a Circle
- Segment of a Circle
- The Interior and the Exterior of a Circle
- Circumcircle of a Triangle
- Incircle of a Triangle
Symmetry (Including Constructions on Symmetry)
- Concept of Symmetry
- Reflection Symmetry in 2-D Shapes
- Construction of Symmetric Points and Lines
Recognition of Solids
- Identification of 3-d Shapes
- Faces, Edges and Vertices of Polyhedron
- Nets of 3D Figures
- Oblique Sketches of 3D Shapes
Perimeter and Area of Plane Figures
- Basic Concepts in Mensuration
- Concept of Perimeter
- Perimeter of a Rectangle
- Perimeter of Squares
- Perimeter of an Equilateral Triangle
- Problems based on Perimeter
- Shapes with the Same Perimeter
- Concept of Area
- Area of Rectangle
- Area of Square
- Problems based on Area
Data Handling (Including Pictograph and Bar Graph)
- Mathematical Data Collection and Organisation
- Frequency Distribution and Its Applications
- Pictographs
- Bar Graphs
Mean and Median
- Concept of Mean (Average)
- Basic Concept of Median

Estimated time: 14 minutes

Introduction
Types of Angles
Activity: Exploring a Straight Angle Using Paper Folding
Key Rotational Benchmarks

CISCE: Class 6

Introduction

An angle is one of the most fundamental ideas in geometry, capturing how two straight lines (or rays) meet at a common point called the vertex.

By measuring the space between these rays in degrees,

we can classify angles into distinct types—zero, acute, right, obtuse, straight, reflex, and full—each with its own unique properties and real-world examples. Understanding these angle classifications builds a crucial foundation for exploring shapes, patterns, and motions in mathematics and beyond.

Maharashtra State Board: Class 5

Angle Type	Angle Range	Description	Illustration
Acute Angle	0° < θ < 90°	An angle that is less than 90°.
Right Angle	θ = 90°	An angle exactly equal to 90°.
Obtuse Angle	90° < θ < 180°	An angle greater than 90° but less than 180°.
Straight Angle	θ=180°	An angle exactly equal to 180°,forming a straight line.
Reflex Angle	180° < θ < 360°	An angle greater than 180° but less than 360°.
Zero Angle	0° ≤ θ ≤ 0°	An angle with a measure of 0 degrees

CBSE: Class 6

Activity: Exploring a Straight Angle Using Paper Folding

Steps:

Take a rectangular piece of paper.
On one of its long sides, mark points A, O, and B to form a straight line AOB (a straight angle).
Fold the paper so that the side OB overlaps exactly on OA.
Press the fold to make a crease passing through point O.
Unfold the paper and observe the two angles formed by the crease.

Observation:

The crease divides the straight angle AOB into two equal angles.
When superimposed, the two angles completely overlap, showing they are equal.
Each of these equal angles measures 90° — a right angle.

Conclusion:

A straight angle (180°) can be divided into two equal right angles (each 90°) by folding.
Hence, a straight angle contains two right angles.

CISCE: Class 6

Key Rotational Benchmarks

Quarter Turn: 90° (Right Angle)
Half Turn: 180° (Straight Angle)
Three-Quarter Turn: 270° (A measure within the Reflex Angle range)
Full Turn: 360° (Complete Angle)

Test Yourself

Class 6 MCQ Test

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Right Angle, Straight Angle, Complete Angle & Reflex Angle Part - 1 [00:16:11]

Types of Angles

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Topics

Number System(Consolidating the Sense of Numberness)

Number System

Estimation

Ratio and Proportion

Algebra

Numbers in India and International System (With Comparison)

Geometry

Place Value

Mensuration

Natural Numbers and Whole Numbers (Including Patterns)

Data Handling

Negative Numbers and Integers

Number Line

HCF and LCM

Playing with Numbers

Sets

Ratio

Proportion (Including Word Problems)

Unitary Method

Fractions

Decimal Fractions

Percent (Percentage)

Idea of Speed, Distance and Time

Fundamental Concepts

Fundamental Operations (Related to Algebraic Expressions)

Substitution (Including Use of Brackets as Grouping Symbols)

Framing Algebraic Expressions (Including Evaluation)

Simple (Linear) Equations (Including Word Problems)

Fundamental Concepts

Angles (With Their Types)

Properties of Angles and Lines (Including Parallel Lines)

Triangles (Including Types, Properties and Constructions)

Quadrilateral

Polygons

The Circle

Symmetry (Including Constructions on Symmetry)

Recognition of Solids

Perimeter and Area of Plane Figures

Data Handling (Including Pictograph and Bar Graph)

Mean and Median

Introduction

Types of Angles

Activity: Exploring a Straight Angle Using Paper Folding

Key Rotational Benchmarks

Test Yourself

Shaalaa.com | Right Angle, Straight Angle, Complete Angle & Reflex Angle Part - 1

Shaalaa.com

Next video

Shaalaa.com

Series: Types of Angles- Acute, Obtuse, Right, Straight, Reflex, Complete and Zero Angle

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