A certain junior class has 1000 students and a certain senior class 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 at random from each class, what is the probability that the 2 students selected will be a sibing pair?
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发表于 2008-6-23 21:45:00
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