Pulling balls out of a box A box has $b$ blue balls and $r$ red balls. We pull the balls without returning them. What is the probability that the $k$th pull is the first red ball and what is the probability that the last ball is red?
Also: do you know a site which fully explains these kinds of problems and all the variation you can have?

The last one is just
$\frac{r}{\left(r+b\right)}$ , no?
And as I commented "Any n'th ball has the red odds I showed above. Last doesn't change the odds" therefore this is the odds for kth ball as well. 
