I have one very, very simple question. How can I calculate the probability of an event if the sample space decreases with every "iteration" of an event?
I'll give an example to make it clear. Suppose that there is a jar of marbles. 30 marbles are white and 5 marbles are red. If I randomly take out two marbles, what is the probability that both of them are white?
Notice that in the first iteration the probability is $30/35$, but in the second one it's $29/34$.