### Mathematics Class IX

Number Systems
Polynomials
Coordinate Geometry
Lines and Angles
Triangles
Circles
Constructions
Heron’s Formula
Surface Areas and Volumes
Statistics
Probability

# Introduction

Non-negative counting numbers excluding zero are called Natural Numbers.

N = 1, 2, 3, 4, 5, ……….

Whole Numbers

All natural numbers including zero are called Whole Numbers.

W = 0, 1, 2, 3, 4, 5, …………

Integers

All natural numbers, negative numbers and 0, together are called Integers.

Z = – 3, – 2, – 1, 0, 1, 2, 3, 4, ………

Rational Numbers

The number ‘a’ is called Rational if it can be written in the form of r/s where ‘r’ and ‘s’ are integers and etc. all are rational numbers.

How to find a rational number between two given numbers?

To find the rational number between two given numbers ‘a’ and ‘b’.

Example:

Find 2 rational numbers between 4 and 5.

Solution:

To find the rational number between 4 and 5

To find another number we will follow the same process again.

Hence the two rational numbers between 4 and 5 are and .

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