8th Class Mathematics Related to Competitive Exam Question Bank Logarithms

  • question_answer
    What is \[\mathbf{lo}{{\mathbf{g}}_{\mathbf{10}}}\left( \frac{\mathbf{3}}{\mathbf{2}} \right)\mathbf{+lo}{{\mathbf{g}}_{\mathbf{10}}}\left( \frac{\mathbf{4}}{\mathbf{3}} \right)\mathbf{+lo}{{\mathbf{g}}_{\mathbf{10}}}\left( \frac{\mathbf{5}}{\mathbf{4}} \right)\mathbf{+}.....\]up to 10 terms equal to?

    A)  0                                

    B)  \[lo{{g}_{10}}6\]

    C)  \[lo{{g}_{10}}5\]                     

    D)  None of these

    Correct Answer: B

    Solution :

               (b): \[{{\log }_{10}}\left( \frac{3}{2} \right)+{{\log }_{10}}\left( \frac{4}{3} \right)+{{\log }_{10}}\left( \frac{5}{4} \right)+....+10th\,\text{term}\] \[={{\log }_{10}}\left( \frac{3}{2} \right)+{{\log }_{10}}\left( \frac{4}{3} \right)+{{\log }_{10}}\left( \frac{5}{4} \right)+....{{\log }_{10}}\left( \frac{12}{11} \right)\] \[={{\log }_{10}}\left( \frac{3}{2}\times \frac{4}{3}\times \frac{5}{4}\times .....\times \frac{12}{11} \right)\] \[={{\log }_{10}}\left( \frac{12}{2} \right)={{\log }_{10}}6\]


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