 # Number System Class 9 Notes - Chapter 1

## What is Number System?

A number system is a system for representing or expressing numbers of a certain type. We can define it as a writing system to express a number. Number system class 9 notes is provided here to help students understand the concepts more effectively.

### Types of Number System

• Binary Number System
• Decimal Number System

## Classification of Number System

### Real Numbers:

Real numbers are numbers which are used to represent the actual physical quantities like height, length, density, weight, etc, in a meaningful figure.

### Rational Number:

Rational numbers are numbers which we can write as a fraction and where the numerator and denominator of the fraction are both whole numbers.

### Irrational Number:

Irrational numbers are numbers which cannot be written as a simple fraction and it cannot be expressed as a ratio between two numbers. An irrational number can be written as a decimal, but not as a fraction.

### Natural Numbers:

The set of positive numbers is called as natural numbers.

### Whole numbers:

Whole numbers are the set of all natural numbers including 0.

### Integers:

The set of all whole numbers along with negative numbers is called as integers.

## Important questions

Q.1) Classify the following numbers as rational or irrational. Q.2) Simplify each of the following expressions:   