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Syllabus

The World of Numbers — Syllabus

CBSE · Class 9 · Mathematics

What The World of Numbers covers in CBSE Class 9 Mathematics: 4 topics, for the 2026-27 session. Part of the CBSE Class 9 Mathematics syllabus.

89 questions76 flashcards10 formulas & key relations5 concepts

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4 Topics · CBSE Class 9 Mathematics · 2026-27

Topics in The World of Numbers

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.

Key Concepts

Central concept: The growth of numbers from counting to real numbers

Natural NumbersHistorical counting evidenceIndian large-number traditionZero and ŚhūnyaIntegersRational NumbersNumber line representationIrrational Numbers

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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.

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All CBSE Class 9 Mathematics Syllabus

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