[理工] 離散-組合問題
抱歉又是小魯..QQ
如圖
http://imgur.com/a/oFttv
(i) Suppose two members of the group of twelve refuse to work in a team,
how many five-person teams can be formed ?
這題讓小魯百思不解為何是 C12取5 - C10取3 ?
根據答案的意思不是就是 "C12取5(所有可能組合) - C10取3(包含此二人之組合)"
意思不就是說 : 那有可能兩人拒絕在團隊裡工作的其中一人可以和剩下10人中的4人
組成一個Team嗎?
可是據題意小魯的解讀是 "此二人不能在5人所形成的Team裡",
故小魯的答案為 : C10取5 (扣除這2人然後再從剩下的10人中取5人組成Team)
(g) Among 11 senators, in how many ways we can select a committee of 5 members
so that at least one of senator A and senator B will be included?
這題也一樣讓小魯想超久....為何是 C11取5 - C9取5 ?
根據答案的意思應該是 : "C11取5(全部可能組合) - C9取5(不包含A和B的組合)"
意思不就是說 : 那有可能僅A或僅B和剩下9人中取4人被選擇嗎?
可是據題意小魯的解讀是
"題目說有at least one of senator A and sentor B "
"所以應該要包括senator A 和 senator B吧??"
故小魯的答案為 : C2取2 (senator A 及 senatro B ) * C9取3 (剩下的9人取3人)
以上這兩題讓小魯想了半個小時快想破頭了
是小魯的英文解讀有誤嗎? 還是題目有瑕疵?
拜託各位大大解惑了!!
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