OK I've been working on a math problem for a while now, and the answer just isn't coming any help would be appreciated. This is for an independent study class. I am basically teaching myself various math subjects that we don't get in school. here it is: Four letters are chosen at random from the word MISSISSIPPI. Determine the probability that at least three I's are chosen. now I know the answer should be (29/330) according to my book, but I can't come up with this answer. It seems to me that the logical thing would be to do this: (4/11)*(3/10)*(2/9)*(1/8)= (1/330) the probability of getting all I's then (4/11)*(3/10)*(2/9)*(1-(1/8))= (7/330) (7/330)+(1/330)= (8/330)= (4/165) I've tried many other things to come up with (29/330) but I can't get that answer any help would be greatly appreciated.