# NCERT Solutions for Class 7 Maths Chapter 9 Exercise 9.2

NCERT Solutions for Class 7 Maths Chapter 9 Exercise 9.2 (Ex. 9.2) Rational Numbers in PDF file format Hindi and English format with videos solution. All the contents are updated as per the latest CBSE Syllabus 2021-2022 CBSE and state board students.

In exercise 9.2 of class vii math, we will practice the questions based on the concept of addition and subtraction of rational numbers taking LCM. Students need little bit more time to practice and become confident in this topic.## Class 7 Maths Chapter 9 Exercise 9.2 Solution

### CBSE NCERT Class 7 Maths Chapter 9 Exercise 9.2 Solution in Hindi and English Medium

Class: 7 | Mathematics |

Chapter: 9 | Rational Numbers |

Exercise: 9.2 | PDF and Videos Solution |

### Class 7 Maths Chapter 9 Exercise 9.2 Solution in Videos

#### Comparison of Rational Numbers

It is clear that:

(i) every positive rational number is greater than 0.

(ii) every negative rational number is less than 0.

##### Compare Two Rational Numbers

Step 1. Express each of the two given rational numbers with positive denominator.

Step 2. Take the LCM of these positive denominators.

Step 3. Express each rational number (obtained in Step 1), with this LCM as the common denominator. Step 4. The number having the greater numerator is greater.

###### Three Important Properties of Rational Numbers

##### Property 1:

For each rational number x, exactly one of the following is true:

(i) x > 0 (ii) x = 0 (iii) x < 0

##### Property 2:

For any two rational numbers x and y. exactly one of the following is true:

(i) x > y (ii) x = y (iii) x < y

##### Property 3:

If x, y and < be rational numbers such that x > y and y > z then x > z.

##### Addition of Rational Numbers

Suppose we have to add two given rational numbers. First convert each of them into a rational number with a positive denominator.

###### CASE-1: When Denominators of Given Numbers are Equal:

Let p/q and r/q be any two rational numbers.

Then, we define (p/q + r/q) = (p + q)/q

Thus, in order to add two rational numbers with the same denominator, we simply add their numerators and divide the sum by the common denominator.

### Class 7 Maths Exercise 9.2 Extra Questions

##### Add 5/9 and -13/9.

We have:

5/9 + (-13)/9 = (5 – 13)/9 = -8/9

CASE-2: When Denominators of Given Numbers are Unequal:

Step 1. Take the LCM of the denominators of the given rational numbers.

Step 2. Express each of the given rational numbers with the above LCM as the common denominator. Step 3. Now, add the numbers as shown in Case I.

##### Add -2/3 and 3/4.

The denominators of the given rational numbers are 3 and 4. LCM of 3 and 4 is 12.

-2/3 = {(-2) x 4}/ (3 x 4) = -8/12

And ¾ = (3 x 3)/ (4 x 3) = 9/12

Now, -8/12 + 9/12 = 1/12

##### Subtract ¾ from 2/3

We have:

2/3 – ¾ = 2/3 + (additive inverse of ¾)

2/3 + -3/4 = (8 -9)/12 = -1/12

##### Subtraction of Rational Numbers

For any two rational numbers a/b and c/d, we define:

a/b – c/d = a/b + (-c/d)

We say that the additive inverse of c/d

a/b – c/d = a/b + additive inverse of c/d

hence, a/b – (-c/d) = a/b + c/d

##### Multiplication of Rational Numbers

The product of two rational numbers is defined below:

Product of two rational numbers = Product of their numerators/ Product of their denominators

Thus, for any rational number a/b and c/d we have:

(a/b x c/d) = (a x c)/ (b x d)

Find the product: 2/3 x 5/7

We have:

2/3 x 5/7 = (2 x 5)/ (3 x 7) = 10/ 21

##### Reciprocal or Multiplicative Inverse of a Rational Number

If the product of two rational numbers is 1 then each one is called the reciprocal of the other.

Thus, the reciprocal of is a/b and b/a we write. a/b = b/a

Clearly, (i) reciprocal of 0 does not exist.

(ii) reciprocal of 1 is 1.

(iii) Reciprocal of -1 is -1.

##### Division of Rational Numbers

If a/b and c/d are two rational numbers such that c/d ≠ 0, then we define:

(a/b)/ (c/d) = a/b x d/c

### Class 7 Maths Exercise 9.2 Important Questions

##### What are the four operations when working with rational numbers?

There are four basic arithmetic operations with rational numbers: addition, subtraction, multiplication, and division.

##### How do you simplify rational numbers?

Step 1: Factor the numerator and the denominator.

Step 2: List restricted values.

Step 3: Cancel common factors.

Step 4: Simplify and note any restricted values not implied by the expression.

##### Why is division not closed for rational numbers?

The rationals are not closed under division because of the possibility of division by zero. Zero is a rational number and division by zero is undefined.