JEE Main & Advanced Mathematics Sequence & Series Question Bank nth term of special series, Sum to n terms and Infinite number of terms

  • question_answer
    The \[{{n}^{th}}\] term of series \[\frac{1}{1}+\frac{1+2}{2}+\frac{1+2+3}{3}+.......\] will be [AMU 1982]

    A) \[\frac{n+1}{2}\]

    B) \[\frac{n-1}{2}\]

    C) \[\frac{{{n}^{2}}+1}{2}\]

    D) \[\frac{{{n}^{2}}-1}{2}\]

    Correct Answer: A

    Solution :

    Given series \[\frac{1}{1}+\frac{1+2}{2}+\frac{1+2+3}{3}+......\] So \[{{n}^{th}}\]term of series is given by \[{{T}_{n}}=\frac{1+2+3+.......+n}{n}=\frac{\frac{1}{2}n(n+1)}{n}=\frac{n+1}{2}\]


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