10th Class Mathematics Real Numbers Question Bank MCQs - Real Numbers

  • question_answer
    The LCM and HCF of two non-zero positive numbers are equal, then the numbers must be:

    A) prime

    B) co-prime

    C) composite

    D) equal

    Correct Answer: D

    Solution :

    Sol.      [d] Let the two numbers be a and b.
    Given, \[HCF(a,b)=LCM(a,b)=k(say)\]
    Since, \[HCF(a,b)=k\Rightarrow a=km\]and \[b=kn,\] for some natural numbers m, n.
    We know, \[HCF\times LCM=\]Product of two numbers         
    \[\therefore \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,k\times k=km\times kn\]
    \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,1=m\cdot n\]
    \[\Rightarrow \,\,\,\,\,\,\,\,\,m=n=1,\]since, m, n are natural numbers.
    Therefore, \[a=km=k\] and \[b=kn=k\]
    \[\Rightarrow \,\,\,\,a=b=k\]i.e., the numbers must be equal.
     


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