Concept-wise Practice

proof reasoning MCQ Questions for Class 10

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Practice Questions

2 questions tagged with proof reasoning.

Question 1/2 Expert Mathematics Chapter 1: Real Numbers 6: Proof of irrationality of √2, √3, √5 Class 10 Level 17

यदि कोई कहे कि \(\sqrt{2}\) अपरिमेय है क्योंकि (2) सम है, तो सही सुधार क्या होगा?

If someone says \(\sqrt{2}\) is irrational because (2) is even, what is the correct correction?

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Correct Answer

A. सम होना अकेले कारण नहीं है; प्रमाण में सरलतम भिन्न का विरोधाभास चाहिएBeing even alone is not the reason; the proof needs contradiction of a lowest-form fraction

Step 1

Concept

The fact that (2) is even is not enough by itself.

Step 2

Why this answer is correct

The real proof assumes \(\sqrt{2}\) rational and shows numerator and denominator both even.

Step 3

Exam Tip

Write the full reason, not a short guess. चरण 1: केवल (2) का सम होना पर्याप्त कारण नहीं है। चरण 2: असली प्रमाण में \(\sqrt{2}\) को परिमेय मानकर अंश और हर दोनों सम निकलते हैं। चरण 3: कारण को पूरा लिखें, छोटा अनुमान नहीं।

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Question 2/2 Medium Mathematics Chapter 1: Real Numbers 6: Proof of irrationality of √2, √3, √5 Class 10 Level 16

एक प्रमाण में \(p^2=2q^2\) से (p=2r) और फिर (q=2s) मिला। यह कौन सा विरोधाभास देता है?

In a proof, from \(p^2=2q^2\), we get (p=2r) and then (q=2s). What contradiction does this give?

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Correct Answer

A. (p) और (q) सहअभाज्य नहीं हैं(p) and (q) are not coprime

Step 1

Concept

(p=2r) and (q=2s) mean both are divisible by (2).

Step 2

Why this answer is correct

So they cannot be coprime.

Step 3

Exam Tip

But they were assumed coprime at the start, which is the contradiction. चरण 1: (p=2r) और (q=2s) से दोनों (2) से विभाज्य हैं। चरण 2: इसलिए वे सहअभाज्य नहीं हो सकते। चरण 3: जबकि शुरुआत में उन्हें सहअभाज्य माना गया था, यही विरोधाभास है।

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