How was this summation simplified to 1/i?

Question

How is the summation below simplified?

$$\sum_{j=i+1}^{2i} \frac1{i^2} = \frac{i}{i^2} = \frac1{i}$$

Thanks!

Answer 1

The summation variable is $j$, not $i$, so you can pull $\frac{1}{i^2}$ outside of the summation giving

$$\sum_{j=i+1}^{2i} \frac{1}{i^2} = \frac{1}{i^2}\sum_{j=i+1}^{2i}1 = \frac{1}{i^2} i = \frac{1}{i}.$$