Chapter 1 · Class 9 ICSE · Formula Sheet
Rational & Irrational Numbers Formulas — Class 9 ICSE
Distinguish between rational and irrational numbers and represent them on the number line.
Key Formulas
Rationalizing
\dfrac{1}{\sqrt{a}} = \dfrac{\sqrt{a}}{a}
Rationalizing Binomial
\dfrac{1}{a + \sqrt{b}} = \dfrac{a - \sqrt{b}}{a^2 - b}
Surds Property
\sqrt{a} \times \sqrt{b} = \sqrt{ab}
Division of Surds
\dfrac{\sqrt{a}}{\sqrt{b}} = \sqrt{\dfrac{a}{b}}
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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