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Railways R.R.C.(Ranchi) Solved Paper Held on 24-11-2013

  • question_answer
    The sum of the first fifteen natural numbers is?

    A) 130                              

    B) 110

    C) 120                              

    D) 140

    Correct Answer: C

    Solution :

    \[\sum n=\frac{n(n+1)}{2}\] \[n=15\] Here           Then, sum of the first 15 natural numbers \[=\frac{15\times (15+1)}{2}\] \[=\frac{15\times 16}{2}=120\]


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