JEE Main & Advanced Mathematics Binomial Theorem and Mathematical Induction Question Bank Expansion of binomial theorem

  • question_answer
    The last digit in \[{{7}^{300}}\] is [Karnataka CET 2004]

    A) 7

    B) 9

    C) 1

    D) 3

    Correct Answer: C

    Solution :

    We have \[{{7}^{2}}=49=50-1\] Now, \[{{7}^{300}}={{({{7}^{2}})}^{150}}={{(50-1)}^{150}}\] = \[^{150}{{C}_{0}}{{(50)}^{150}}{{(-1)}^{0}}+{{\,}^{150}}{{C}_{1}}{{(50)}^{149}}{{(-1)}^{1}}+......\]\[+{{\,}^{150}}{{C}_{150}}{{(50)}^{0}}{{(-1)}^{150}}\] Thus the last digits of \[{{7}^{300}}\] are \[^{150}{{C}_{150}}.1.1\] i.e., 1.


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