David Mashley teaches two undergraduate statistics courses at Kansas College.The class for Statistics 201 consists of 7 sophomores and 3 juniors.The more advanced course,Statistics 301,has 2 sophomores and 8 juniors enrolled.As an example of a busine

David Mashley teaches two undergraduate statistics courses at Kansas College.The class for Statistics 201 consists of 7 sophomores and 3 juniors.The more advanced course,Statistics 301,has 2 sophomores and 8 juniors enrolled.As an example of a business sampling technique,professor Mashley randomly selects,from the stack of Statistics 201 registration card,the class card of one student and then places that card back in the stack.If that student was a sophomore,Mashley draws another card from the Statistics 201 stack; if not,he randomly draws a card from the statistics 301 group.Are these two draws independent events?What is the probability of:
a) A junior's name on the first draw?
b) A junior's name on the second draw,given that a sophomore's name was drawn first?
c) A junior's name on the second draw,given that a junior's name was drawn first?
d) A sophomore's name on the both draws?
e) A junior's name on the both draws?
f) One sophomore's name and one junior's name on the two draws,regardless of order drawn?

a) 3/(3+7)=3/10
b)junior's name on the second draw : 7/10×3/10+3/10×8/10=9/20
junior's name on the second draw and a sophomore's name was drawn first:7/10×3/10=21/100
(21/100)/(9/20)=7/15
c) junior's name on the second draw : 7/10×3/10+3/10×8/10=9/20
A junior's name on the second draw and a junior's name was drawn first: 3/10×8/10=6/25
(6/25)/(9/20)=8/15
d)7/10×7/10=49/100
e) 3/10×8/10=6/25
f) 7/10×3/10+3/10×2/10=27/100
PS:楼上的你given 没有翻译.而且是大二生不是高中生.

嘿嘿本人英语好，但数学可是一塌糊涂。 让我来翻译吧！ 其实这道题目就是个可能性－ － 。 david 叫两个还没毕业的班级。班级201要7个高中生和3个初中生。另个班级，更为优秀（算是尖子班） 班级301要有2个高中生和8个初中生。所以呢他要从抽取201班级的学生，要随意抽一张学生的卡又放回去。如果那个学生是个高中生，david就又要从201的抽箱中抽1位，但如果那学生不是高中生，那么david就...

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嘿嘿本人英语好，但数学可是一塌糊涂。 让我来翻译吧！ 其实这道题目就是个可能性－ － 。 david 叫两个还没毕业的班级。班级201要7个高中生和3个初中生。另个班级，更为优秀（算是尖子班） 班级301要有2个高中生和8个初中生。所以呢他要从抽取201班级的学生，要随意抽一张学生的卡又放回去。如果那个学生是个高中生，david就又要从201的抽箱中抽1位，但如果那学生不是高中生，那么david就要从301箱中随意抽选一位。问：这两个抽选的概率相等吗？以下问题是问你每个的可能性。
a） 第一次抽到的是个初中生
b）第二次抽到的是个初中生，第一次抽到的是高中生。
c） 第二次抽到的是个初中生，第一次抽到的也是初中生
d） 两次抽到的都是同一个高中生
e）两次抽到的都是同一个初中生
f） 不确定，sorry。

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you did not say that "7 sophomores and 3 juniors"和"2 sophomores and 8 juniors enrolled"的card 数量是否一样，所以我感觉你是否少说了什么条件。或者说the two events are independent completely .They are not related at all.

晕哈，哥们不是我不帮你，中文的我解，但英语藕看不懂