Railways Sample Paper RRBs Assistant Loco Pilot and Technician CBT STAGE-I Sample Paper-15

  • question_answer
    If a, b, c are in HP, then \[{{4}^{-a}},{{4}^{-b}},{{4}^{-c}}\] are

    A)  GP                  

    B)  HP

    C)  AP                  

    D)  None of these

    Correct Answer: D

    Solution :

    \[\because a,b,c\]are in HP, then b \[=\frac{2ac}{(a+c)}\] (i) \[{{4}^{-b}}\ne \frac{1}{2}({{4}^{-a}}+{{4}^{-c}})\] \[{{4}^{-a}},{{4}^{-b}},{{4}^{-c}}\] are not in AP. (ii) \[{{4}^{-2b}}\ne {{4}^{-a}}\times {{4}^{-c}}\] \[\Rightarrow \]   \[2b\ne (a+c)\] \[{{4}^{-a}},{{4}^{-b}},{{4}^{-c}}\] are not in GP. \[{{4}^{-b}}\ne \frac{2\cdot {{4}^{-a}}\cdot {{4}^{-c}}}{{{4}^{-a}}+{{4}^{-c}}}\] \[{{4}^{-a}},{{4}^{-b}},{{4}^{-c}}\]are not in HP. Hence, \[{{4}^{-a}},{{4}^{-b}},{{4}^{-c}}\] are neither in AP nor in GP nor in HP.


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