What Is the Sum of the Series \( \sum_{n=1}^\infty \frac{n}{(n+1)!} \)?

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SUMMARY

The sum of the series \( \sum_{n=1}^\infty \frac{n}{(n+1)!} \) converges to 1. The sequence of partial sums is given by \( S_1 = \frac{1}{2} \), \( S_2 = \frac{5}{6} \), \( S_3 = \frac{23}{24} \), \( S_4 = \frac{119}{120} \), and \( S_5 = \frac{719}{720} \). By observing the pattern in the partial sums, one can conjecture that \( S_n = 1 - \frac{1}{(n+1)!} \). This can be proven using mathematical induction, and taking the limit as \( n \) approaches infinity confirms that the sum equals 1.

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Find the sum of this series:
$$ \sum_{n=1}^\infty \frac{n}{(n+1)!} $$

I'm really struggling with this one.. Any help will be highly appreciated. Thanks you.
 
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Look at the sequence of partial sums.

$$S_1 = \dfrac{1}{2}$$, $$S_2 = \dfrac{5}{6}$$, $$S_3 = \dfrac{23}{24}$$, $$S_4 = \dfrac{119}{120}$$, $$S_5 = \dfrac{719}{720}$$, etc.

Once you guess the obvious answer for $$S_n$$, you can prove it by induction. Then take the limit as $$n \rightarrow \infty$$
 

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