In a certain board game, a stack of 48 cards, 8 of which represent shares of stock, are shuffled and then placed face down.If the first 2 cards selected do not represent shares of stock, what is the probability that the third card selected will represent a share of stock?
我是这样想的： 2C40 * 1C8/(3C48)
可是算完后没有答案
据说答案是 4/23
谁能帮我分析一下我错在哪里了。。。谢谢 作者: season5924 时间: 2011-5-2 20:46
They ask for "what is the probability that the third card selected will represent a share of stock." So you only focus on the drawing of the third card and do not worry about the chance of all three card's makeup. Therefore, there are 8 "stock"cards among the 46 cards. To get one of the eight cards, you chance is 8/46 = 4/23.
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