Question

一道GMAT数学题

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 student is to be selected at random from each class ,what is the probability that the 2 students selected will be a sibling pair ?

(A)3/40,000
(B)1/3,600
(C)9/2,000
(D)1/60
(E)1/15

Answer 1

从这些学生中选两人每班选一人的可能情况数：1000*800
从sibling pair中选一对的可能数：60
概率就是3/40000

Answer 2

一定的初级类有1000名学生和一个特定的高级类有800名学生。这些学生中,有60个兄弟姐妹组成的对,每1初级和1高级。如果学生是随机选择从每个类,什么是概率,2学生选择将一个兄弟对吗?