Question: User: how to find this $\frac{1}{50}+\frac{1}{100}+...+\frac{1}{505}+\frac{1}{510}$
1. **State the problem:** We want to find the sum of the series $$\frac{1}{50}+\frac{1}{100}+\cdots+\frac{1}{505}+\frac{1}{510}$$ where the denominators increase by 5 each time starting from 50 up to 510.
2. **Identify the terms:** The terms are $$\frac{1}{50}, \frac{1}{55}, \frac{1}{60}, \ldots, \frac{1}{505}, \frac{1}{510}$$ because the denominators increase by 5.
3. **Number of terms:** To find the number of terms, use the formula for an arithmetic sequence:
$$n = \frac{\text{last term} - \text{first term}}{\text{step}} + 1 = \frac{510 - 50}{5} + 1 = \frac{460}{5} + 1 = 92 + 1 = 93$$
4. **Sum of the series:** The sum is
$$S = \sum_{k=0}^{92} \frac{1}{50 + 5k}$$
5. **No simple closed form:** This sum does not simplify nicely to elementary functions, so we approximate by calculating each term or using numerical methods.
6. **Approximate sum:** Calculate each term and add or use a numerical tool to find the approximate value.
**Final answer:** The sum is $$\sum_{k=0}^{92} \frac{1}{50 + 5k}$$ which can be approximated numerically.