按双琴的话，得先补英文，再补数学

来源: 姜申 于 2020-05-19 10:30:05 [] [博客] [旧帖] [给我悄悄话] 阅读数 : (555 bytes)
本帖于 2020-05-19 10:31:21 时间, 由普通用户 姜申 编辑
回答: 土了吧，这是条件概率 ：） 由 网恋无罪 于 2020-05-19 10:16:00

Bag A has 2 white marbles, Bag B contains 2 black marbles, Bag C contains one white marble and one black marble.

He picks a bag RANDOMLY and takes out ONE marble. It is a white marble.

the question

"What is the probability that the reamining marble from the same bag is also white?”

is the same question as:

"What is the probability that the first marble is from Bag A?"

.

end of story.

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