Chapter 3 · Class 8 CBSE · Formula Sheet

Rational Numbers Formulas — Class 8 CBSE

Study properties of rational numbers: closure, commutativity, distributivity.

Key Formulas

Closure (Addition)

\dfrac{a}{b} + \dfrac{c}{d} \in \mathbb{Q}

Closure (Multiplication)

\dfrac{a}{b} \times \dfrac{c}{d} \in \mathbb{Q}

Additive Inverse

\dfrac{a}{b} + \left(-\dfrac{a}{b}\right) = 0

Multiplicative Inverse

\dfrac{a}{b} \times \dfrac{b}{a} = 1

Rational Between Two Rationals

\text{Mean} = \dfrac{1}{2}\left(\dfrac{a}{b} + \dfrac{c}{d}\right)

Worked Examples

1Using: Place Value

Find the place value of 6 in 3,65,421.

Step 1: 6 is in the ten-thousands place.

Step 2: Place value = 6 x 10,000 = 60,000.

Answer: 60,000

2Using: Successor

Find the successor of 9,999.

Step 1: Successor = n + 1

Step 2: = 9,999 + 1 = 10,000.

Answer: 10,000

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More Class 8 CBSE Formulas

Squares, Cubes & Their RootsExponents & PowersQuadrilateralsNumber Patterns & PuzzlesAlgebraic Expressions & IdentitiesDirect & Inverse Proportions

Frequently Asked Questions

How many formulas are in Class 8 CBSE Rational Numbers?+
There are 5 formulas in the Rational Numbers chapter for Class 8 CBSE. Each formula is essential for solving problems in this topic.
How to remember Rational Numbers formulas easily?+
Practice regularly with worked examples, group related formulas together, and use SparkEd's interactive practice mode to reinforce your memory through problem-solving.
Are these Rational Numbers formulas enough for exams?+
Yes, these formulas cover the complete CBSE Class 8 syllabus for Rational Numbers. Practice applying them to different types of questions for full exam readiness.

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