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A certain junior class has 1000 students and a certain [#permalink]
20 May 2006, 04:45
A certain junior class has 1000 students and a certain senior class has 800 students. Among these students, there are 60 sibling pairs eac consisting 1 junior and 1 senior. If 1 student is to be selected at random from each class, what is the probabilty that the 2 students selected will be a sibling pair?