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Question Hard Mathematics Chapter 1: Real Numbers 5: Irrational numbers Class 10 Level 14

किस विकल्प में संख्या निश्चित रूप से अपरिमेय है?

In which option is the number definitely irrational?

Explanation opens after your attempt
Correct Answer

B. \(4\sqrt{7}\)

Step 1

Concept

\(0\times\sqrt{7}=0\), \(\sqrt{7}\times\sqrt{7}=7\), and \(\sqrt{28}\div\sqrt{7}=2\) are rational.

Step 2

Why this answer is correct

\(4\sqrt{7}\) is a non-zero rational multiple of an irrational number, so it is irrational.

Step 3

Exam Tip

Quickly identify multiplication by zero as rational. चरण 1: \(0\times\sqrt{7}=0\), \(\sqrt{7}\times\sqrt{7}=7\), और \(\sqrt{28}\div\sqrt{7}=2\) परिमेय हैं। चरण 2: \(4\sqrt{7}\) में अशून्य परिमेय गुणक और अपरिमेय मूल है, इसलिए यह अपरिमेय है। चरण 3: शून्य से गुणा वाले विकल्प को जल्दी परिमेय पहचानें।

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