JEE Main & Advanced AIEEE Solved Paper-2004

  • question_answer
    \[\underset{n\to \infty }{\mathop{\lim }}\,\sum\limits_{r=1}^{n}{\frac{1}{n}{{e}^{r/n}}}\]is

    A) \[e\]    

    B)                        \[e-1\]                 

    C)        \[1-e\]                 

    D)        \[e+1\]

    Correct Answer: B

    Solution :

    \[\underset{n\to \infty }{\mathop{\lim }}\,\sum\limits_{r=1}^{n}{\frac{1}{n}}{{e}^{r/n}}=\int_{0}^{1}{{{e}^{x}}}dx\] Now, \[\underset{n\to \infty }{\mathop{\lim }}\,\sum\limits_{r=1}^{n}{\frac{1}{n}}{{e}^{r/n}}=\int_{0}^{1}{{{e}^{x}}}dx=[{{e}^{x}}]_{0}^{1}=e-1\]


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