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7th Class Mathematics Exponents and Power Question Bank Exponents and Power

  • question_answer
    \[{{\left\{ {{3}^{-2}}+{{\left( \frac{3}{2} \right)}^{-2}} \right\}}^{-1}}=?\]

    A) \[{}^{81}/{}_{4}\]                              

    B)  \[{}^{5}/{}_{9}\]

    C) \[\frac{9}{5}\]                          

    D) \[\frac{4}{81}\]

    Correct Answer: C

    Solution :

    (c) \[{{3}^{-2}}=\frac{1}{{{3}^{2}}}=\frac{1}{9},\]\[=\frac{1}{{{\left( {}^{3}/{}_{2} \right)}^{2}}}=\frac{1}{{}^{9}/{}_{4}}=\frac{4}{9}\] \[={{\left( \frac{1}{9}+\frac{4}{9} \right)}^{-1}}={{\left( \frac{5}{9} \right)}^{-1}}=\frac{9}{5}\]        


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