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Mathematics

Proof of irrationality of square root 2 and square root 3

√2 और √3 की अपरिमेयता का प्रमाण

In Class 9 Mathematics, this Number Systems topic explains how to prove that √2 and √3 are irrational numbers. Students use proof by contradiction: they assume a square root can be written as a fraction in lowest terms, then apply prime-factor and divisibility properties to show that the assumption leads to an impossibility. The lesson strengthens understanding of rational and irrational numbers, factors, parity, and the logic of mathematical proof, while helping learners present each step clearly and accurately.

TOPIC PRACTICE

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Medium · Level 17 · number-systems,irrationality-proof,coprime
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  1. To prove (p=q)
  2. So that (p) and (q) are coprime
  3. So that (q=0) can be written
  4. So that decimal can be found
Medium · Level 17 · number-systems,contradiction-method,sqrt2
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  1. (\sqrt{2}) is irrational
  2. (\sqrt{2}) is an integer
  3. (\sqrt{2}) is rational
  4. (\sqrt{2}) is zero
Medium · Level 17 · number-systems,sqrt3,divisibility
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  1. Because (p=q)
  2. Because (q=0)
  3. Because (p) is even
  4. Because (p^2) is divisible by (3), so (p) is divisible by (3)
Medium · Level 17 · number systems, irrational numbers, proof by contradiction, square root 3, coprime integers
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  1. Both \(p\) and \(q\) are divisible by 3.
  2. Only \(p\) is even.
  3. \(q\) is greater than \(p\).
  4. Both \(p\) and \(q\) are prime.
Medium · Level 17 · number-systems,sqrt3,contradiction-step
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  1. (q) is even
  2. (q) is divisible by (3)
  3. (q=0)
  4. (p=q)
Medium · Level 17 · number systems, irrational numbers, proof by contradiction, square root 3, coprime integers
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  1. \(p\) is divisible by 3, but no conclusion can be drawn about \(q\).
  2. \(q\) is divisible by 3, but no conclusion can be drawn about \(p\).
  3. \(p\) is divisible by 3; on putting \(p=3k\), \(q\) is also proved divisible by 3, contradicting coprimality.
  4. Both \(p\) and \(q\) must be odd integers.
Medium · Level 17 · number systems,square root 3,irrationality proof,coprime numbers,contradiction proof
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  1. From \(p^2=3q^2\), \(p^2\) is divisible by \(3\)
  2. If \(p^2\) is divisible by \(3\), then \(p\) is divisible by \(3\)
  3. Even if both \(p\) and \(q\) are divisible by \(3\), they are coprime
  4. Getting common factor \(3\) in both is a contradiction
Medium · Level 17 · number systems, irrational numbers, square roots, perfect squares, proof of irrationality
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  1. 16
  2. 36
  3. 50
  4. 64
Medium · Level 17 · number-systems,sqrt3,final-conclusion
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  1. (\sqrt{3}) is rational
  2. (\sqrt{3}) is zero
  3. (\sqrt{3}) is irrational
  4. (\sqrt{3}) is an integer
Medium · Level 17 · number systems,proof of irrationality,square root 2,Proof of irrationality of square root 2 and square root 3,Mathematics,Class 9 MCQ
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  1. (m²=2n²), (m) even, (m=2r), (n) even
  2. (m²=3n²), (m=3r), (n) divisible by (3)
  3. (m=n), (n=0), contradiction
  4. (m) odd, (n) odd, conclusion
Medium · Level 17 · number systems,proof of irrationality,square root 3,Proof of irrationality of square root 2 and square root 3,Mathematics,Class 9 MCQ
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  1. (p²=2q²), (p) even, (q) even
  2. (p=q), (q=0), conclusion
  3. (p²=3q²), (p) divisible by (3), (p=3k), (q) divisible by (3)
  4. (p) negative, (q) negative, contradiction
Medium · Level 17 · number systems, irrational numbers, proof by contradiction, square root 3, coprime integers
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  1. q cannot be a multiple of 3 because q² is a square
  2. k and q must be coprime
  3. p² must be equal to q²
  4. q is divisible by 3; therefore p and q have a common factor 3
Medium · Level 17 · number systems, irrational numbers, square root 3, proof by contradiction, rational numbers
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  1. Showing that \(\sqrt{3}\) is positive
  2. Showing that 3 lies between 1 and 4
  3. Writing 3 in decimal form
  4. Assuming \(\sqrt{3}=\frac{m}{n}\) in lowest terms and deriving a contradiction
Medium · Level 17 · number-systems,rational-form,sqrt2
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  1. (m,n) coprime and (n\neq0)
  2. Both (m,n) even
  3. (n=0)
  4. (m=n)
Medium · Level 17 · number systems, irrational numbers, proof by contradiction, square root 2, coprime integers, parity
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  1. He must also prove that \(n\) is even, contradicting that \(m\) and \(n\) are coprime.
  2. He must prove that \(m\) is odd.
  3. He must prove that \(n\) is odd.
  4. He must write the decimal expansion of \(\sqrt{2}\) up to at least 20 places.
Medium · Level 17 · number systems, irrational numbers, proof by contradiction, square root 3, coprime integers
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  1. \(p\) is divisible by 3, but no conclusion can be drawn about \(q\).
  2. Both \(p\) and \(q\) are divisible by 3.
  3. \(q\) is divisible by 3, but \(p\) is not divisible by 3.
  4. Neither \(p\) nor \(q\) is divisible by 3.
Medium · Level 17 · number systems,divisibility by 3,proof reasoning,Proof of irrationality of square root 2 and square root 3,Mathematics,Class 9 MCQ
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  1. If (p²) is divisible by (3), then (p) is divisible by (2)
  2. If (p²) is divisible by (3), then (p) is divisible by (3)
  3. If (p²) is divisible by (3), then (p=0)
  4. If (p²) is divisible by (3), then (p=q)
Medium · Level 17 · number systems,square root 2,contradiction proof,Proof of irrationality of square root 2 and square root 3,Mathematics,Class 9 MCQ
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  1. Rational assumption makes both (m) and (n) even
  2. Decimal terminates
  3. (m=n) is proved
  4. (n=0) is proved
Medium · Level 17 · number-systems,sqrt3,final-basis
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  1. Decimal terminates
  2. Rational assumption makes both (p) and (q) divisible by (3)
  3. (p=q) is proved
  4. (q=0) is proved
Medium · Level 17 · number-systems,sqrt2,error-analysis
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  1. It is correct because (n) is even first
  2. It is incomplete because (m) must be proved even first
  3. It is correct because (n=0)
  4. It is correct because (m=n)