CBSE Class 8 Maths Revision Notes Chapter 1 – Rational Numbers -CoolGyan

Revision Notes for CBSE Class 8 Maths Chapter 1 – Free PDF Download

Free PDF download of Class 8 Maths Chapter 1 – Rational Numbers Revision Notes & Short Key-notes prepared by expert Maths teachers from latest edition of CBSE(NCERT) books. All Chapter 1 – Rational Numbers Revision Notes to help you to revise complete Syllabus and Score More marks.
Maths NCERT Solutions for Class 8

Chapter Name	Rational Numbers
Chapter	Chapter 1
Class	Class 8
Subject	Maths Revision Notes
Board	CBSE
TEXTBOOK	CBSE NCERT
Category	Revision Notes

Quick Revision Notes

Rational numbers are closed under the operations of addition, subtraction and multiplication.
The operations addition and multiplication are
(i) commutative for rational numbers.
(ii) associative for rational numbers.
The rational number 0 is the additive identity for rational numbers.
The rational number 1 is the multiplicative identity for rational numbers.
The additive inverse of the rational number $\frac{a}{b}$ is $\frac{a}{b}$ and vice-versa.
The reciprocal or multiplicative inverse of the rational number $\frac{a}{b}$ is $\frac{c}{d}$ if $\frac{a}{b}$ x $\frac{c}{d}$ =1
Distributivity of rational numbers: For all rational numbers a, b and c,
a(b + c) = ab + ac and a(b – c) = ab – ac
Rational numbers can be represented on a number line.
Between any two given rational numbers there are countless rational numbers. The idea of mean helps us to find rational numbers between two rational numbers.
Positive Rationals: Numerator and Denominator both are either positive or negative. Example: $\frac{4}{7}, \frac{- 3}{- 4}$
Negative Rationals: Numerator and Denominator both are of opposite signs. Example: $\frac{- 2}{11}, \frac{4}{- 9}$
Additive Inverse: Additive inverse (negative) $\frac{a}{b}$ + $\frac{- a}{b}$ = $\frac{- a}{b}$ + $\frac{a}{b}$ =0, $\frac{- a}{b}$ is the additive inverse of $\frac{a}{b} a n d \frac{a}{b}$ is the additive inverse of $\frac{- a}{b}$ .
Mulitiplicative Inverse (reciprocal): $\frac{a}{b}$ x $\frac{c}{d}$ =1= $\frac{c}{d}$ x $\frac{a}{b}$ where $\frac{c}{d}$ is the reciprocal of $\frac{a}{b}$ . Zero has no reciprocal. The reciprocal of 1 is1 and of -1 is -1.