8th Class Mathematics Exponents and Power Question Bank Exponents and Powers

  • question_answer
    Solve for y, if \[\frac{{{\left( \frac{1}{9} \right)}^{2y-1}}{{(.0081)}^{1/3}}}{\sqrt{243}}={{\left( \frac{1}{3} \right)}^{2y-5}}\sqrt[3]{\frac{{{27}^{y-1}}}{10000}}\]

    A)  \[\frac{1}{2}\]                                   

    B)  \[-\frac{19}{18}\]     

    C)  \[\frac{3}{10}\]                     

    D)         \[\frac{12}{17}\]       

    Correct Answer: B

    Solution :

    We have, \[\frac{{{({{3}^{-2}})}^{2y-1}}{{({{3}^{4}}\cdot {{10}^{-4}})}^{1/3}}}{{{3}^{5/2}}}=\frac{{{3}^{-(2y-5)}}\cdot {{3}^{3\left( \frac{y-1}{3} \right)}}}{{{10}^{4/3}}}\] \[\Rightarrow \frac{{{3}^{-4y+2+\frac{4}{3}-\frac{5}{2}}}}{{{10}^{4/3}}}=\frac{{{3}^{-2y+5+y-1}}}{{{10}^{4/3}}}\] \[\Rightarrow {{3}^{-4y+\frac{5}{6}}}={{3}^{-y+4}}\] On comparing, we get \[-4y+\frac{5}{6}=-y+4\] \[\Rightarrow -3y=4-\frac{5}{6}\Rightarrow -3y=\frac{24-5}{6}\] \[\Rightarrow y=\frac{-19}{18}\]


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