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Railways Sample Paper RRB (Group D) Sample Test Paper-13

  • question_answer
    Which one of the following will completely divide \[{{5}^{71}}+{{5}^{72}}+{{5}^{73}}?\]

    A)  150                 

    B)  160

    C)  155                 

    D)  30

    Correct Answer: C

    Solution :

    [c] \[{{5}^{71}}+{{5}^{72}}+{{5}^{73}}\] \[={{5}^{73}}(1+5+{{5}^{2}})={{5}^{70}}\times 5\times 31\] \[={{5}^{71}}\times 155\] Which is exactly divisible by 155.


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