Number Systems

8 Topics | 8 Quizzes

6 Topics | 8 Quizzes

Introduction

Polynomials in One Variable

Zeros of a Polynomial

Remainder Theorem

Factorization of Polynomials

Algebraic Identities

Practice Questions 5 – Polynomials – Class IX

Concept Checkers – Polynomials – Class IX

Practice Questions 1 – Polynomials – Class IX

Practice Questions 2 – Polynomials – Class IX

Practice Questions 3 – Polynomials – Class IX

Practice Questions 4 – Polynomials – Class IX

Olympiad Questions – Polynomials – Class IX

Olympiad Questions 2 – Polynomials – Class IX

Coordinate Geometry

3 Topics | 4 Quizzes

Introduction

Quadrants of the Cartesian Plane

Coordinates of a Point

Concept Checkers – Coordinate Geometry – Class IX

Practice Questions – Coordinate geometry – Class IX

Olympiad Questions – Coordinate Geometry – Class IX

Olympiad Questions 2 – Coordinate Geometry – Class IX

Linear Equations in Two Variables

5 Topics | 7 Quizzes

Linear Equations

Solutions of a Linear Equation

Graph of a Linear Equation in Two Variables

Equations of Lines Parallel to x-axis and y-axis

Summary

Practice Questions 3 – Linear equation in two variables – Class IX

Practice Questions 4 – Linear equation in two variables – Class IX

Concept Checkers – Linear Equations in two variables – Class IX

Practice Questions 1 – Linear Equations in two variables – Class IX

Practice Questions 2 – Linear Equations in two variables – Class IX

Olympiad Questions – Linear Equations in two varaibles – Class IX

Olympiad Questions 2 – Linear Equation in two variables – Class IX

Introduction to Euclid’s Geometry

3 Topics | 4 Quizzes

Introduction

Euclid’s Definitions, Axioms and Postulates

Equivalent Versions of Euclid’s Fifth Postulate

Concept Checkers – Introduction to Euclid’s Geometry – Class IX

Practice Questions – Introduction to Euclid’s geometry – Class IX

Olympiad Questions – Introduction to Euclid’s Geometry – Class IX

Olympiad Questions 2 – Introduction to Euclid’s geometry – Class IX

Lines and Angles

7 Topics | 6 Quizzes

Basic Terms and Definitions

Intersecting Lines and Non-Intersecting Lines

Pair of Angles

Parallel Lines and a Transversal

Lines Parallel to the same Line

Angle Sum Property of a Triangle

Summary

Concept Checkers – Lines and Angles – Class IX

Practice Questions 1 – Lines and Angles – Class IX

Practice Questions 2 – Lines and Angles – Class IX

Practice Questions 3 – Lines and angles – Class IX

Olympiad Questions – Lines and Angles – Class IX

Olympiad Questions 2 – Lines and angles – Class IX

Triangles

5 Topics | 4 Quizzes

Introduction

Congruence of Triangles

Criteria for Congruence of Triangles

Some Properties of a Triangle

Inequalities in a Triangle

Concept Checkers – Triangles – Class IX

Practice Questions – Triangles – Class IX

Olympiad Questions – Triangle – Class IX

Olympiad Questions 2-Triangles-Class IX

Quadrilaterals

5 Topics | 5 Quizzes

Introduction

Angle Sum Property of a Quadrilateral

Types of Quadrilateral

Properties of a Parallelogram

The Mid-Point Theorem

Concept Checkers – Quadrilaterals – Class IX

Concept Checkers2-Quadrilaterals-ClassIX

Practice Questions-Quadrilaterals-ClassIX

Olympiad Questions – Quadrilaterals – Class IX

Olympiad Questions 2-Quadrilaterals-Class IX

Areas of Parallelogram and Triangles

5 Topics | 4 Quizzes

Introduction

Figure on the same Base and Between the same Parallels

Parallelograms on the same Base and Between the same Parallels

Triangles on the same Base and Between the same Parallels

Summary

Concept Checkers-Areas of Parallelograms and Triangles-ClassIX

Practice Questions- Areas of Parallelograms and Triangles-Class IX

Olympiad Questions – Areas of Parallelograms and Triangles – Class IX

Olympiad Questions 2-Areas of Parallelogram and Triangles-Class IX

Circles

5 Topics | 4 Quizzes

Introduction

Terms related to circle

Angles Subtended by a Chord at a Point

Angle Subtended by an Arc of a Circle

Cyclic Quadrilaterals

Concept Checkers 2-Circles-Class IX

Olympiad Questions 2-Circles-Class IX

Practice Questions-Circle-Class IX

Olympiad Questions-Circles-Class IX

Constructions

4 Topics | 3 Quizzes

Introduction

Basic Constructions

Some Constructions of Triangles

Summary

Practice Questions-Constructions-Class IX

Essay Type Questions-Constructions-Class IX

Concept Checkers-Construction-Class IX

Heron’s Formula

4 Topics | 4 Quizzes

Introduction

Area of a Triangle – by Heron’s Formula

Application of Heron’s Formula in Finding Areas of Quadrilaterals

Summary

Concept Checkers 2- Heron’s Formula-Class IX

Olympiad Questions 2-Herons Formula-Class IX

Concept Checkers-Heron’s formula-Class IX

Olympiad Questions-Heron’s formula-Class IX

Surface Areas and Volumes

5 Topics | 2 Quizzes

Introduction

Surface Area and Volume of a Cube

Surface Area and Volume of a Right Circular Cylinder

Surface Area and Volume of a Right Circular Cone

Surface Area and Volume of a Sphere

Practice Questions-Surface Areas and Volume-Class IX

Olympiad Questions – Surface Areas and Volume – Class IX

Statistics

5 Topics | 2 Quizzes

Introduction

Collection of Data

Geographical Representation of Data

Measures of Central Tendency

Summary

Practice Questions-Statistics-Class IX

Olympiad Questions-Statistics-Class IX

Probability

3 Topics | 4 Quizzes

Introduction

Probability – An Experimental Approach

Summary

Concept Checkers 2-Probability-Class IX

Olympiad Questions 2-Probability-Class IX

Olympiad Questions-Probability-Class IX

Practice Questions-Probability-Class IX

Next Topic

Angle Sum Property of a Quadrilateral

Mathematics Class IX Quadrilaterals Angle Sum Property of a Quadrilateral

The sum of the four angles of a quadrilateral is 360°

If we draw a diagonal in the quadrilateral, it divides it into two triangles.

And we know the angle sum property of a triangle i.e. the sum of all the three angles of a triangle is 180°.

The sum of angles of $\mathrm{\triangle ADC = 180^o}$ .

The sum of angles of $\mathrm{\triangle ABC=180^o}$ .

By adding both we get $\mathrm{\angle A + \angle B + \angle C + \angle D = 360^o}$

Hence, the sum of the four angles of a quadrilateral is 360°.

Example

Find $\angle$ A and $\angle$ D, if BC || AD and $\angle$ B = 52° and $\angle$ C = 60° in the quadrilateral ABCD.

Solution:

Given BC ∥ AD, so ∠A and ∠B are consecutive interior angles.

So $\angle$ A + $\angle$ B = 180° (Sum of consecutive interior angles is 180°).

$\angle$ B = 52°

$\angle$ A = 180°- 52° = 128°

$\angle$ A + $\angle$ B + $\angle$ C + $\angle$ D = 360° (Sum of the four angles of a quadrilateral is 360°).

$\angle$ C = 60°

128° + 52° + 60° + $\angle$ D = 360°

$\angle$ D = 120°

$\therefore\angle$ A = 128° and $\angle$ D = 120°.

Previous Topic

Back to Lesson

Next Topic