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# [Core] Probabilities

## Probabilities

There are 7 sports channels and 5 movie channels available for subscription. 4 channels are randomly selected from these channels to subscribe to.  Find the probability that

a) a particular movie channel is selected

b) the numbers of sports channels and movie channels selected are the same.

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 風之男 學院師父 發短消息 加為好友 當前離線 2# 大 中 小 發表於 2020-12-12 12:20 AM (第 192 天) 只看該作者 [顯示] [隱藏] Hints: (a) Let's rephrase the question a bit. Let's say we have 7 sports channels, 4 generic movie channels and "Movie 1" (for a total of 12 channels). We still pick 4 channels from the 12. What is the probability that "Movie 1" is selected? (b) Presumably you have learned combinatorics (nPr and nCr), use it to tackle it. Remember probability is just "Number of Preferred Cases/Total Number of Cases", if you're lost with the multiplying/adding probabilities line of thought. (b) is a very standard question. Try to understand it fully. Ask further if you're still stuck. UID216418 帖子931 精華0 積分114 閱讀權限40 在線時間1553 小時 註冊時間2011-5-4 最後登錄2021-6-22  查看詳細資料 TOP
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