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Probability關於要乘整數問題(急!!!!!!!!!
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我想問probability幾時要係個分數乘個整數呢？例如呢條數:Stem(tens) Leaf(units) 1 2 5 5 7 8 2 4 4 4 4 5 6 7 9 3 2 2 2 2 5 5 5 6 8 4 2 3Find the probability that the mean score of the two students is the same as the mean score of the 24 students. (mean score is 28)Ans: Let x and y be... 顯示更多 我想問probability幾時要係個分數乘個整數呢？例如呢條數: Stem(tens) Leaf(units) 1 2 5 5 7 8 2 4 4 4 4 5 6 7 9 3 2 2 2 2 5 5 5 6 8 4 2 3 Find the probability that the mean score of the two students is the same as the mean score of the 24 students. (mean score is 28) Ans: Let x and y be their marks. (x+y)/2=28 x+y=56 Possible combinations: (18,38) (24,32), (27,29) Probability: 2x(1/24x1/23)+2x (4/24x4/23)+2x (1/24x1/23) =3/46 為什麼要在分數之前乘一個整數2 呢？
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Probability關於要乘整數問題(急!!!!!!!!!
發問:
我想問probability幾時要係個分數乘個整數呢？例如呢條數:Stem(tens) Leaf(units) 1 2 5 5 7 8 2 4 4 4 4 5 6 7 9 3 2 2 2 2 5 5 5 6 8 4 2 3Find the probability that the mean score of the two students is the same as the mean score of the 24 students. (mean score is 28)Ans: Let x and y be... 顯示更多 我想問probability幾時要係個分數乘個整數呢？例如呢條數: Stem(tens) Leaf(units) 1 2 5 5 7 8 2 4 4 4 4 5 6 7 9 3 2 2 2 2 5 5 5 6 8 4 2 3 Find the probability that the mean score of the two students is the same as the mean score of the 24 students. (mean score is 28) Ans: Let x and y be their marks. (x+y)/2=28 x+y=56 Possible combinations: (18,38) (24,32), (27,29) Probability: 2x(1/24x1/23)+2x (4/24x4/23)+2x (1/24x1/23) =3/46 為什麼要在分數之前乘一個整數2 呢？
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可能既組合有(18,38)(24,32)(27,29) 唔知你留唔留意到 依3個組合都各自可以用2種方法組成 (18,38) 可以先抽18之後抽38,亦可能係(38,18) 先抽38 後抽18 2個都係同1個組合黎,所以就要將機率x2 例如有1個組合係(1,2,3) ,呢個組合就有3!=6個可能,所以如果係呢個情況下就要將呢個prob x 6. 例如個組合係(12,13,13) 咁呢個組合就有3個可能組成,所以就要x3 睇返你果個表,如果係加埋係70,咁就有(35,35)既可能 咁呢個可能得1個組合,抽邊個先都係一樣,所以呢個組合就唔洗x啦~ 再唔明就寫信問我~其他解答:
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