The question is as follows:
Consider the two uniform random variables $X$ on the interval $[0, n]$ and $Y$ on the interval $[0, X]$. What is the expected value of $Y$?
My idea was to find the expected value of $E[X]$ of $X$ and then let $Y$ be on the interval $[0, E[X]]$, but I fear this is horribly wrong. Can somebody please help?