NTSE Sample Paper NTSE SAT Practice Test-9

  • question_answer
    If \[{{2}^{x}}={{3}^{y}}={{6}^{-z}}\], then \[\left( \frac{1}{x}+\frac{1}{y}+\frac{1}{z} \right)\] is equal to:                 

    A) 0            

    B) 1

    C) \[\frac{3}{2}\]                          

    D) \[-\frac{1}{2}\]

    Correct Answer: A

    Solution :

    [a] \[{{2}^{x}}={{3}^{y}}={{6}^{-z}}=k\,\,(say)\] \[\Rightarrow \,2={{k}^{\frac{1}{x}}};3={{k}^{\frac{1}{y}}}\,\,and\,\,6={{k}^{-\frac{1}{z}}}\] \[6=2\times 3={{k}^{\frac{1}{x}}}.{{k}^{\frac{1}{y}}}={{k}^{\frac{1}{x}+\frac{1}{y}}}\] \[\Rightarrow k\left( \frac{1}{x}+\frac{1}{y} \right)={{k}^{-\frac{1}{z}}}\] \[\therefore \,\,\frac{1}{x}+\frac{1}{y}=-\frac{1}{z}\,\,or\,\,\frac{1}{x}+\frac{1}{y}+\frac{1}{z}=0.\]                 


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