EDUVISTA GOLDEN MASTER NOTES • CLASS 9 MATHEMATICS
Chapter 1: Number Systems
Selected Chapter Revision Notes | Real Numbers, Rationalisation & Exponents
👨‍🏫 Prepared by Abhishek Sir 🎯 Target: CBSE Board Exams & School Finals 👑 Black & Gold Luxury Edition

These are selected revision notes and practice questions. No original exam-year or paper references have been verified; these questions are not presented as authenticated past papers. Use your current textbook and teacher guidance for complete coverage.

1. Real Number Classification Hierarchy

Real Numbers ($\mathbb{R}$)
→
Rationals ($\mathbb{Q} = p/q, q \neq 0$)
→
Irrationals ($\sqrt{2}, \pi$, Non-terminating Non-repeating)

2. Key Formulas & Theorem Summary

Master Rules Laws of Real Exponents

2.1 Rationalization of Denominator

To eliminate surds (square roots) from the denominator, multiply both numerator and denominator by the conjugate of the denominator.

Example: Rationalize $\frac{1}{\sqrt{7} - \sqrt{6}}$

$$\frac{1}{\sqrt{7} - \sqrt{6}} \times \frac{\sqrt{7} + \sqrt{6}}{\sqrt{7} + \sqrt{6}} = \frac{\sqrt{7} + \sqrt{6}}{(\sqrt{7})^2 - (\sqrt{6})^2} = \frac{\sqrt{7} + \sqrt{6}}{7 - 6} = \sqrt{7} + \sqrt{6}$$

3. Selected Revision Practice Questions

PRACTICE Q1: Express $0.\overline{235}$ in the form $\frac{p}{q}$. (3 Marks)

Solution: Let $x = 0.235235235\dots$ (Eq 1).
Since 3 digits repeat, multiply both sides by $1000$:
$1000x = 235.235235\dots$ (Eq 2).
Subtracting Eq 1 from Eq 2:
$999x = 235 \implies x = \frac{235}{999}$.