9th Class Mathematics Related to Competitive Exam Question Bank Logarithms

  • question_answer
    If \[{{\log }_{r}}6=m\] and \[lo{{g}_{r}}3=n\] then is \[lo{{g}_{r}}\left( r/2 \right)\]is equal to

    A)  \[m-n+1\]        

    B)  \[m+n-1\]           

    C)  \[m-n-1\]                      

    D)  \[m-n+1\]

    Correct Answer: D

    Solution :

    (d): Given, \[lo{{g}_{r}}6=m\text{ }and\text{ }lo{{g}_{r}}3=n\] \[\therefore lo{{g}_{r}}6-lo{{g}_{r}}\left( 2\times 3 \right)\] \[=lo{{g}_{r}}2\text{ }+lo{{g}_{r}}3\] \[\therefore lo{{g}_{r}}3+lo{{g}_{r}}2=m\] \[\Rightarrow n+lo{{g}_{r}}2=m\] \[\Rightarrow lo{{g}_{r}}2=m-n\] \[=1-m+n\]


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