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ZWMath›Real analysis›Real numbers›Density of the rationals›ZW-DENSITY-OF-THE-RATIONALS-008
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AreaAnalysisCourseReal analysisTopicReal numbers
Real numbers6
  • Ordered field
  • Supremum and infimum
  • Completeness axiom
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  • Density of the rationals
Sequences7
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  • Uniqueness of limits
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  • Monotone convergence theorem
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Limits and continuity6
  • Limit of a function Calculus
  • Continuous function Calculus
  • Sequential continuity
  • Intermediate value theorem Calculus
  • Extreme value theorem Calculus
  • Uniform continuity
Differentiation5
  • Derivative Calculus
  • Differentiability and continuity
  • Rolle's theorem Calculus
  • Mean value theorem Calculus
  • L'Hôpital's rule Calculus
Integration and series8
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  • Fundamental theorem of calculus Calculus
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Exercise · ZW-DENSITY-OF-THE-RATIONALS-008 · ★★☆ Intermediate

Which of these numbers between \(1\) and \(2\) is irrational?

Choose one option.

Show answer
  • A. \(\sqrt2\)

← Back to the question

Explanation

\(\sqrt2\approx1.414\) lies between \(1\) and \(2\) and is irrational; the other three are fractions.

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Review the concept: Density of the rationals

Property of the rationals \(\mathbb Q\) inside the reals: between any two distinct reals \(a<b\) there is always a rational \(q\).

\[a

More practice problems: density of the rationals

  • ZW-DENSITY-OF-THE-RATIONALS-001 Between any two distinct reals there is always:
  • ZW-DENSITY-OF-THE-RATIONALS-002 Which rational lies between tfrac13 and tfrac12?
  • ZW-DENSITY-OF-THE-RATIONALS-003 Which rational lies between √2 and √3?
  • ZW-DENSITY-OF-THE-RATIONALS-004 Is there a positive rational smaller than all the others?
  • ZW-DENSITY-OF-THE-RATIONALS-005 Which number lies between 0.999 and 1?
  • ZW-DENSITY-OF-THE-RATIONALS-006 The rational midpoint of tfrac27 and tfrac37 is:
  • ZW-DENSITY-OF-THE-RATIONALS-007 In the density proof with a=0.3 and b=0.4, take n=11 with tfrac1n<b-a and m=lfloor narfloor+1. Whic…
  • ZW-DENSITY-OF-THE-RATIONALS-009 Between two reals a<b there are:

← ZW-DENSITY-OF-THE-RATIONALS-007 ZW-DENSITY-OF-THE-RATIONALS-009 →

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