Q: there are 8 red, 9 green and 6 yellow cards in a pack of cards. Five cards are drwan. Find the probability of obtaining 2 red and 3 green cards if it is known that at least one card is green
I don't get the restriction of the question "if it is known that at least one card is green"
the answer is , i don't get the part is the total number of ways of choosing 5 cards from 23, 14 is from 23-9,
1. I don't get the "at least" part and how it ties in with
The total number of ways of drawing 5 cards is 23C5.
The total number of ways of drawing 5 cards, none of which is green, is 14C5.
So the total number of ways of drawing 5 cards of which at least one of them is green is 23C5-14C5.
and you would be wrong.
(there is a clue you can use to determine if you should answer a question or not, it is: If you find your self typing "I think XXXXX is ..." and you can't replace this by "XXXXX is ..". You may ignore this clue if the question has been around for a few days and not been answered by someone who knows.)
CB