Skip to main content
Super TutorResources
Chapter 3 of 8
Revision Notes

The World of Numbers — Revision Notes

CBSE · Class 9 · Mathematics

The World of Numbers revision notes for CBSE Class 9 Mathematics: 4 topics in quick points. Part of the CBSE Class 9 Mathematics syllabus.

89 questions76 flashcards10 formulas & key relations5 concepts

Interactive on Super Tutor

Studying The World of Numbers? Get the full interactive chapter.

Quizzes, flashcards, AI doubt-solver and a step-by-step study plan — built for revision notes and more.

Try Super Tutor — Free

Free trial, no card needed.

Key Topics to Revise

1

1. Growth of Number Systems

  • Natural numbers are the counting numbers {1, 2, 3, 4, ...}.
  • Natural numbers came from one-to-one correspondence in counting objects.
  • Natural numbers are closed under addition.
2

2. Zero and Integers

  • Zero was formally transformed into a number by Brahmagupta in 628 CE in the Brāhmasphuṭasiddhānta.
  • The chapter summary gives Brahmagupta's formalisation of zero as 629 CE.
  • Brahmagupta defined zero as a - a = 0.
3

3. Rational Numbers

  • Rational numbers are denoted by Q for quotient.
  • A rational number can be written in the form p/q where p and q are integers and q is not zero.
  • Rational numbers include integers, whole numbers, and fractions.
4

4. Irrational Numbers

  • Irrational numbers cannot be written as a ratio of integers.
  • Irrational numbers have non-terminating, non-repeating decimal expansions.
  • Baudhāyana composed the Shulbasūtra around 800 BCE and encountered lengths that defied fractions.

Get complete notes with diagrams and examples

Full Notes

Key Concepts

Natural numbers are the counting numbersThe Lebombo Bone has 29 notchesZero became a formal operational numberIntegers are the set {The basic rules are a +

Frequently Asked Questions

What are the important topics in The World of Numbers for CBSE Class 9 Mathematics?
Key topics in The World of Numbers include Growth of Number Systems, Zero and Integers, Rational Numbers, Irrational Numbers. Study these first, then practise questions on each for Class 9 exams.
How should I revise The World of Numbers for Class 9 exams?
Learn the core ideas first, then work through the 89 practice questions on The World of Numbers. Revise definitions regularly and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

More resources for The World of Numbers

All CBSE Class 9 Mathematics Revision Notes

For serious students

Get the full The World of Numbers chapter — start free.

Quizzes, flashcards, an AI doubt solver and a study plan for CBSE Class 9 Mathematics. Free to start, no card needed.

Try Super Tutor Free
Try this chapter free