Manipal Engineering Manipal Engineering Solved Paper-2011

  • question_answer
    The value of\[\log \,\,2+2\left( \frac{1}{5}+\frac{1}{3}\cdot \frac{1}{{{5}^{3}}}+\frac{1}{5}\cdot \frac{1}{{{5}^{5}}}+.... \right)\], is

    A) \[\log 2+\log 3\]              

    B)        \[\log 2+2\]

    C) \[\frac{1}{2}\log 2\]       

    D)        \[\log 3\]

    Correct Answer: D

    Solution :

    \[\log 2+2\left( \frac{1}{5}+\frac{1}{3}\cdot \frac{1}{{{5}^{3}}}+\frac{1}{5}\cdot \frac{1}{{{5}^{5}}}+...\infty  \right)\]                 \[=\log 2+\log \left( \frac{1+\frac{1}{5}}{1-\frac{1}{5}} \right)\]                 \[=\log 2+\log \left( \frac{3}{2} \right)=\log 3\]


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