Question

一题GRE数学题

谁能告诉我这个题是怎么算的，题目具体是什么意思？
A university admitted 100 students who transferred from other institutions. Of these students, 34 transferred from two-year community colleges, 25 transferred from private four-year institutions, and the rest transferred from public four-year institutions. If two different students are to be selected at random from the 100 students, what is the probability that both students selected will be students who transferred from two-year community colleges?
答案是17/150，我觉得是17/50啊。可能是问题理解错了吧，求帮助！

Answer 1

两年制的有34人，私立四年的有25人，公立四年的有100-34-25=41人，
然后用概率C2 3除以C2 100，（我打不出来公式）即 34*33除以100*99为17/150
这是数学题，不关英语的事，你英语已经很好了

Answer 2

两个人全是两年制公立学校的选法是34*33/（1*2）；
总的可能选法是100*99/（1*2）；
相处，即为可能性33*34/（99*100）=17/150

Answer 3

你好
两年制的有34人，私立四年的有25人，公立四年的有100-34-25=41人，
然后用概率C2 3除以C2 100，（我打不出来公式）即 34*33除以100*99为17/150

Answer 4

这是一道排列题目，首先从100个人中选任选两个总共有100*99/2*1种方法，然后这两个人都来自两年制公立学校，即从34人中任选两个，共有34*33/2*1种方法，那么这种情况发生的概率就是33*34/（99*100）=17/150

Answer 5

select 2 students from 100 students, the number of ways is 100*99/2
select 2 students from 34 students from two-year community colleges, the number of ways is 34*33/2
thus the asked probability is (34*33/2)/(100*99/2)=17/150