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Railways Sample Paper RRB (Assistant Loco Pilot) Sample Test Paper-16

  • question_answer
    The unit's digit in the product \[({{7}^{71}}\times {{6}^{59}}\times {{3}^{65}})\] is:

    A)  1                                

    B)  2                                

    C)  4                                

    D)  6

    Correct Answer: C

    Solution :

    Unit digit in \[{{7}^{4}}\] is 1. Unit digit in \[{{7}^{68}}\] is 1. \[\therefore \]  Unit digit in \[{{7}^{71}}=1\times {{7}^{3}}=3\] Again, every power of 6 will give unit digit 6. \[\therefore \]Unit digit in 659 is 6. Unit digit in 34 is 1. \[\therefore \]Unit digit in 364 is 1. Unit digit in 365 is 3. \[\therefore \] Unit digit in \[({{7}^{71}}\times {{6}^{59}}\times {{3}^{65}})\] = Unit digit in \[(3\times 6\times 3)=4.\]


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