A certain junior class has 1,000 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 sibling pair?
这道题应该怎么做呢？
PRER上木有 答案作者: cckjenius 时间: 2011-5-12 06:44
In total, there are 1000 X 800 = 800000 combinations.
and there are only 60 combinations which are sibling paris.
So the probability is 60/800000作者: haileywang 时间: 2011-5-13 20:53
