There are 4 red, 2 white, and 4 blue marbles in an urn. Two marbles are selected at random without replacement. What is the probability that neither is red, given that neither is white?
I said it was 2/5ths since there are 10 marbles in all, you don't want them red OR white, which leaves you with the 4 blue marbles.
4/10 = 2/5
However this seems to be the wrong answer. Would someone mind explaining what I did wrong?
EDIT: SOLVED IT. I didn't factor in that white was the given.