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Railways Sample Paper RRB (Group D) Sample Test Paper-10

  • question_answer
    Of the three numbers, the first is twice the second, and the second is twice the third. The average of the reciprocal of the numbers is 7/12. The numbers are:

    A)  20, 10, 5         

    B)  4, 2, 1

    C)  36, 18, 9         

    D)  16, 8, 4

    Correct Answer: C

    Solution :

    [c] Let third number =x Then, Second number = 2x First number = 4 x According to question \[\frac{\left( \frac{1}{x}+\frac{1}{2x}+\frac{1}{4x} \right)}{3}=\frac{7}{12}\] \[\therefore \,\,\,x=9\] \[\therefore \]First number \[=4x=4\times 9=36\] Second number \[=2x=2\times 9=18\] Third number = x = 9


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