1 probability question

2017/06/21 05:50

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1 probability question

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there are 32 stds in a class. Their students nos are numbered from 1 to 32. a teacher chooses 3 stds from std nos'1-10',3 from'11-20' and 4 from 21-32 as members of class representatives randomly. the std nos of Sarah and Christy are 4 and 27 sparately. find the prob. that both of them become... 顯示更多 there are 32 stds in a class. Their students nos are numbered from 1 to 32. a teacher chooses 3 stds from std nos'1-10',3 from'11-20' and 4 from 21-32 as members of class representatives randomly. the std nos of Sarah and Christy are 4 and 27 sparately. find the prob. that both of them become members of class representatives.

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there are 32 stds in a class. Theirstudents nos are numbered from 1 to 32. a teacher chooses 3 stds from std nos'1-10',3 from'11-20' and 4 from 21-32 as members ofclass representatives randomly. the std nos of Sarah and Christy are 4 and 27sparately. find the prob. that both of them become members of class representatives. Sol 1~10=>3 11~20=>3 21~32=>4 So P(no4)=3/10 P(no27)=4/12=1/3 (3/10)*(1/3)=1/10