# NCERT Book Class 9th Maths Chapter 1 Number System PDF Download

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PDF Name Number System – NCERT Book Class 9th Maths Chapter 1 24 1.8 MB English PDF PREVIEW

## Introduction to Class 9th Maths Chapter 1

The Class 9th Maths Chapter 1 begins with a brief overview of the number line and how to represent various types of numbers on it. It then delves into different types of numbers, including natural numbers, whole numbers, integers, rational numbers, and irrational numbers.

The chapter also covers decimal expansions and how to classify them as terminating or non-terminating recurring or non-recurring decimals. Number System Class 9 PDF serves as a foundation for understanding more advanced topics in mathematics.

## What will you learn from this chapter?

In this Class 9th Maths Chapter 1, You will learn about the different types of numbers and their representation on a number line. The chapter covers various types of numbers, such as rational and irrational numbers, and provides insights on distinguishing between them by examining their decimal expansions.

You will also learn how to recognize between rational and irrational numbers using their decimal expansions.

### What is a number line and how is it used to represent different types of numbers?

A number line is a straight line that represents all real numbers. It is used to represent different types of numbers by placing them at the appropriate position on the line.

### What are natural numbers, whole numbers, integers, rational numbers, and irrational numbers?

Natural numbers are positive integers (1, 2, 3, …), whole numbers are non-negative integers (0, 1, 2, …), integers include both positive and negative whole numbers (…-2, -1, 0, 1, 2,…), rational numbers can be expressed as a ratio of two integers (p/q where q ≠ 0), and irrational numbers cannot be expressed as a ratio of two integers.

### How can we classify decimal expansions as terminating or non-terminating recurring or non-recurring decimals?

A decimal expansion is terminating if it ends after a finite number of digits (e.g., 0.25). A decimal expansion is non-terminating recurring if it repeats a pattern of digits after some point (e.g., 0.333…). A decimal expansion is non-terminating non-recurring if it does not repeat any pattern of digits (e.g., pi = 3.14159265358979323846…).

### Can zero be considered a rational number? Why or why not?

Yes, zero can be considered a rational number because it can be expressed as p/q where p = 0 and q ≠ 0.

### What are some examples of irrational numbers?

Examples of irrational numbers include pi (π), e (the base of natural logarithms), and the square root of any non-perfect square.

### How can we find rational numbers between two given rational numbers?

To find rational numbers between two given rational numbers, we can take their average and simplify the resulting fraction.

### How do we know if a given number is a whole number or an integer?

A number is a whole number if it is a non-negative integer, and it is an integer if it can be expressed as a ratio of two integers.

### Why is it important to understand different types of numbers and their properties?

Understanding different types of numbers and their properties is important because it helps us solve problems in various fields such as mathematics, science, engineering, and finance.

### Is zero a rational number?

Yes, zero is a rational number. It can be written in the form p/q, where p and q are integers and q ≠ 0.

### Can you find six rational numbers between 3 and 4?

Yes, we can find six rational numbers between 3 and 4. For example, (7/2), (13/4), (15/4), (17/4), (19/4), and (23/6).