The World of Numbers Exercise 3.2 Class 9 Maths NCERT Solutions

This page solves The World of Numbers Exercise 3.2 from the new Ganita Manjari book of the 2026-27 syllabus. The NCERT Solutions Class 9 Maths Chapter 3 The World of Numbers Exercise 3.2 add and subtract integers on the number line and use Brahmagupta's sign rules, each shown in short and clear steps.

• Questions solved: all 4 problems of Exercise 3.2, with full working.
• Main skills: adding and subtracting integers and applying the sign rules.
• Chapter link: these sign rules power the rational-number work later in the chapter.

These solutions are prepared by subject teachers, matched to the 2026-27 NCERT, and checked step by step so a Class 9 student can follow each line.

What Does Class 9 Maths Chapter 3 The World of Numbers Exercise 3.2 Cover?

Exercise 3.2 works with integers using real debt and credit stories. You add and subtract positive and negative numbers, using a Ladakh temperature record and a spice trader's loan. The set then states Brahmagupta's sign laws for multiplying and dividing. It closes with a short explanation of why subtracting a negative means adding.

Integers appear in almost every later topic, so this exercise is worth real care. A temperature that drops below zero, a loan that must be repaid, and a balance that swings between profit and loss are all integer problems in disguise. Once you can add and subtract signed numbers without slips, Brahmagupta's rules for multiplying and dividing follow quickly. The same sign rules then carry straight into rational numbers, algebra, and graphs. Getting them firm now saves time in every exercise that comes after this one, and it protects easy marks in the annual exam.

Video Walkthrough

Source: Vedantu CBSE 10th on YouTube

The World of Numbers Exercise 3.2 Question Breakdown

The four questions move from real-life integers to the formal sign rules. Here is what each one asks.

• Q1: A Ladakh temperature record is used to add and subtract integers.
• Q2: A spice trader takes a debt of 850 rupees, and you track his balance.
• Q3: You calculate four expressions using Brahmagupta's sign laws.
• Q4: You explain, with a debt example, why subtracting a negative gives addition.

Sample Solved Question from Exercise 3.2

Here is Question 3 of Exercise 3.2, solved step by step so you can see the sign rules in action.

Question: Calculate using Brahmagupta's laws: (i) (-12)× 5, (ii) (-8)×(-7), (iii) 0-(-14), (iv) (-20)÷ 4.

Step 1. For (-12)× 5, the signs are unlike, so the answer is negative. Multiply the plain values: 12× 5 = 60. So the result is -60.

Step 2. For (-8)×(-7), both signs are negative, so the answer is positive. Multiply the plain values: 8× 7 = 56. So the result is +56.

Step 3. For 0-(-14), subtracting -14 is the same as adding 14. So 0-(-14) = 0 + 14 = 14.

Step 4. For (-20)÷ 4, the signs are unlike, so the answer is negative. Divide the plain values: 20÷ 4 = 5. So the result is -5.

Final answer. The four answers are -60, +56, 14, and -5.

How to Use These The World of Numbers Exercise 3.2 Solutions

Solve each part on paper first, then open the Collegedunia solution to check your signs. Careful sign work here saves marks in every later exercise.

• Write the sign rule before you multiply or divide, then fill in the plain value.
• Remember that two minuses give a plus only for multiplication and division, not addition.
• Download the free Collegedunia PDF to revise Exercise 3.2 offline.

More Class 9 Maths The World of Numbers Solutions

Use the table below to open the full chapter page or any other exercise of Class 9 Maths Chapter 3.