I need to find what definite integral is approximated by $\displaystyle \sum_{i=1}^{50} (\frac{i}{50})^2\frac{1}{50}$ on the interval [0,1]

the answer seems to be $\displaystyle \int_0^1 x^2dx$ but why is it not $\displaystyle \int_0^1\frac{x^2}{50^3}dx$

Do I only concern myself with what is happening to i or whatever variable is used, i, k etc etc

thanks