JEE Main & Advanced Mathematics Functions Question Bank Limits

  • question_answer
    \[\underset{n\to \infty }{\mathop{\lim }}\,\left\{ \frac{1}{{{n}^{2}}}+\frac{2}{{{n}^{2}}}+\frac{3}{{{n}^{2}}}+......+\frac{n}{{{n}^{2}}} \right\}\]is [SCRA 1996]

    A)                 ½

    B)                 0

    C)                 1

    D)                 \[\infty \]

    Correct Answer: A

    Solution :

                       \[\underset{n\to \infty }{\mathop{\lim }}\,\,\left( \frac{1}{{{n}^{2}}}+\frac{2}{{{n}^{2}}}+\frac{3}{{{n}^{2}}}+.......+\frac{n}{{{n}^{2}}} \right)\]                    \[=\underset{n\to \infty }{\mathop{\lim }}\,\,\,\left( \frac{1+2+3+......+n}{{{n}^{2}}} \right)=\underset{n\to \infty }{\mathop{\lim }}\,\,\frac{\frac{n}{2}(n+1)}{{{n}^{2}}}\]                                 \[=\frac{1}{2}\,\,\underset{n\to \infty }{\mathop{\lim }}\,\,\,\frac{n+1}{n}=\frac{1}{2}\,\,\underset{n\to \infty }{\mathop{\lim }}\,\,\,1+\frac{1}{n}=\frac{1}{2}\]


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