JEE Main & Advanced Mathematics Binomial Theorem and Mathematical Induction Question Bank Self Evaluation Test - Binomial Theorem

  • question_answer
    The fractional part of \[\frac{{{2}^{4n}}}{15}\] is

    A) \[\frac{1}{15}\]

    B) \[\frac{2}{15}\]

    C) \[\frac{4}{15}\]

    D) None of these

    Correct Answer: A

    Solution :

    [a] \[\frac{{{2}^{4n}}}{15}=\frac{{{16}^{n}}}{15}=\frac{{{(1+15)}^{n}}}{15}\] \[=\frac{1+{{\,}^{n}}{{C}_{1}}\,15+{{\,}^{n}}{{C}_{2}}\,{{15}^{2}}+....+{{\,}^{n}}{{C}_{n}}\,\,{{15}^{n}}}{15}\] \[=\frac{1+15\,k}{15},\] where \[k\in N,=\frac{1}{15}+k\] \[\therefore \] Fractional part of \[\frac{{{2}^{4n}}}{15}\] is \[\frac{1}{15}\]


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