SSC Sample Paper Mock Test-1 SSC CGL Tear-II Paper-1

  • question_answer
    If q is the mean proportional between p and r, \[\frac{{{p}^{2}}-{{q}^{2}}+{{r}^{2}}}{{{p}^{-2}}-{{q}^{-2}}+{{r}^{-2}}}\]then is equal to               

    A)  \[{{p}^{2}}{{q}^{3}}\]                    

    B)  \[{{q}^{3}}\]

    C)  \[{{q}^{4}}\]

    D)  \[{{p}^{2}}{{r}^{2}}{{q}^{2}}\]

    Correct Answer: C

    Solution :

    As, given \[{{q}^{2}}\] = pr \[\frac{{{p}^{2}}-{{q}^{2}}+{{r}^{2}}}{{{p}^{-2}}-{{q}^{-2}}+{{r}^{-2}}}=\]\[\frac{{{p}^{2}}-{{q}^{2}}+{{r}^{2}}}{\frac{1}{{{p}^{2}}}-\frac{1}{{{q}^{2}}}+\frac{1}{{{r}^{2}}}}=\]\[\frac{{{p}^{2}}-{{q}^{2}}+{{r}^{2}}}{\frac{{{r}^{2}}-pr+{{p}^{2}}}{{{p}^{2}}{{r}^{2}}}}\] \[=\frac{({{p}^{2}}{{r}^{2}})({{p}^{2}}-{{q}^{2}}+{{r}^{2}})}{({{r}^{2}}-pr+{{p}^{2}})}=\frac{({{p}^{2}}{{r}^{2}})({{p}^{2}}-pr+{{r}^{2}})}{({{r}^{2}}-pr+{{p}^{2}})}\] \[={{p}^{2}}{{r}^{2}}={{(pr)}^{2}}={{({{q}^{2}})}^{2}}={{q}^{4}}\]


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