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

  • question_answer
    Pairs of natural numbers whose least common multiple is 78 and the greatest common divisor is 13 are:

    A) 58 and 13 or 16 and 29

    B) 68 and 23 or 36 and 49

    C) 18 and 73 or 56 and 93

    D) 78 and 13 or 26 and 39

    Correct Answer: D

    Solution :

    Sol.      [d] Let numbers are 13x and 13y where x and y are coprime.
                \[\therefore \,\,\,\,\,\,\,\,\,\,\,\,LCM=13\times x\times y=78\]
                            \[x\times y=6\]
    \[\therefore \]  Possible values of x and y                          
                \[x=1,\,\,\,y=6,\,\,x=2,\,\,y=3\]
    \[\therefore \] Pairs of natural numbers are 78 and 13 or 26 and 39.


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