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标题: princeton 系統里的數學題. [打印本页]

作者: dc9259 时间: 2010-8-16 14:41
标题: princeton 系統里的數學題.
There are two boxes of markers. The first box has only red, orange and yellow markers. The second box has only yellow, green and blue markers. If a marker is chosen at random from each of the boxes, is the probability that both markers will be yellow less than 30%?
(1)Four of the 12 total markers are yellow.
(2)The probability of selecting a red or orange marker is

and the probability of selecting a green or blue marker is

.
第一個情況, 無論盒一和盒二的筆子總數是9-3, 8-4, 7-5, 6-6的分佈, 2枝都是黃的機率都是小於30%. 我選了D做答案但他們的正確是B. 算來算去都找不到什麼的配搭在(1) 里會出現高於30%.
有什麼看法呢大家?

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