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

  • question_answer
    Simplify\[\frac{{{\left( 9{{a}^{2}} \right)}^{1/2}}\times {{\left( 25{{a}^{4}} \right)}^{\frac{-1}{2}}}}{5{{a}^{1/2}}\times 3{{a}^{1/2}}\times 4{{a}^{9/4}}}\]

    A)  \[100\,{{a}^{\frac{25}{4}}}\]             

    B)  \[\frac{1}{100{{a}^{\frac{21}{4}}}}\]

    C) \[20{{a}^{\frac{-21}{4}}}\]                 

    D)  \[20\,{{a}^{\frac{21}{4}}}\]

    Correct Answer: B

    Solution :

    (b) \[\frac{{{\left( 9{{a}^{2}} \right)}^{\frac{1}{2}}}\times {{\left( 25{{a}^{4}} \right)}^{-1/2}}}{5\times 3\times 4\times {{a}^{\frac{1}{2}+\frac{3}{2}+\frac{9}{4}}}}\] \[=\frac{{{\left( {{3}^{2}}{{a}^{2}} \right)}^{\frac{1}{2}}}\times {{\left( {{5}^{2}}{{a}^{4}} \right)}^{\frac{-1}{2}}}}{60{{a}^{17/4}}}=\frac{3a\times {{5}^{-1}}{{a}^{-2}}}{60{{a}^{17/4}}}\] \[=\frac{3{{a}^{-1}}}{5\times 60\times {{a}^{17/4}}}\] \[=\frac{{{a}^{\frac{-21}{4}}}}{100}\] \[=\frac{1}{100{{a}^{\frac{21}{4}}}}\]


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