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数学一题 谢谢大家
A certain junior class has 1000 students and a cetain senior has 800 students.Among these students , there are 60 sibling pairs,each consisting of 1 junior and 1 senior.If 1 student is to be selected random from each class, what is the possibilty that the 2 students selected will be a sibiling pair.
答案 3/40000
为什么 |
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