8th Class Mathematics Logarithms Question Bank Logarithms

  • question_answer The value of log3 81 is equal to:

    A)  -27                              

    B)  -4

    C)  4                                

    D)  27

    Correct Answer: B

    Solution :

    (b): Let \[\text{lo}{{\text{g}}_{(-1/3)}}81=x.\] Then, \[{{\left( -\frac{1}{3} \right)}^{x}}=81={{(-3)}^{4}}={{\left( -\frac{1}{3} \right)}^{-4}}\] \[\therefore x=-4\,\,i.e.,\,\,\text{lo}{{\text{g}}_{(-1/3)}}81=-4\]

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