作者collegeman (通体舒畅)
看板GRE_Verbal
标题Re: [计量] CAT (机率问题)
时间Mon Oct 13 23:39:46 2008
※ 引述《ELASTOMER (恶性循环........)》之铭言：
: 题目是
: If a bowl contains seven marbles, three red and four
: green, four marbles are drawn from the bowl at random
: without replacement. What is the propability that contains
: two red marbles and two green ones?
: 答案是18/35 不知要怎麽解,麻烦各位帮我解答一下,谢谢
C(3,2) x C(4,2)
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C(7,4)
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