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  3. RAJASTHAN ­ PET

RAJASTHAN ­ PET Rajasthan PET Solved Paper-2009

  • question_answer
    Let a, b, c are in GP and 4a,5b,4c are in AP such that\[a+b+c=70,\]then value of\[b\]is

    A)  5     

    B)  10     

    C)  15     

    D)  20

    Correct Answer: D

    Solution :

     Given a, b, c are in GP and 4a, 5b, 4c are in AP \[\therefore \] \[{{b}^{2}}=ac\] and \[5b=\frac{4a+4c}{2}\] \[\Rightarrow \] \[{{b}^{2}}=ac\] and \[5b=2a+2c\] Now,        \[a+b+c=70\]        (Given) \[\Rightarrow \] \[2a+2c+2b=140\] \[\Rightarrow \]   \[5b+2b=140\] \[\Rightarrow \] \[b=20\]


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