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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 two students selected will be a sibling pair?
This problem is fairly old and I have read the previous posts' explanations. But I'm still really confused about one thing.
So the probability of picking the first member of the sibling pair from the junior class is 60/1000. But how come the probability of picking the other member of the sibling pair from the senior class is 1/800?
I mean after you find the first guy from the junior class, you still need to find his brother/sister in the senior class, and you have to look for this person in that 60 pair siblings sample don't you?
I don't understand why the possibility becomes 1/800 for that second member of the sibling pair? Why are you saying this person could be 1 of 800 kids when he is very well 60 of 800 kids?
Thanks! Needs enlightenments desperately...I'm going about this the wrong way surely.
Taking the GMAT in five days. CRAM TIME! Should have started preparing sooner