Well first I'll throw out all these guys with low GPA's,

我首先会排出GPA较低的同学
so they can all sit down and

你们这些同学请坐
I'll look at these last three and these last three,

下面我们来关注一下剩下的三名同学
if they're all in the group they better all have the same GPA.

如果他们都被选中了则他们的GPA相等
Why on earth?

这是为什么呢
If I'm trying to maximize the average of my group,

如果我想尽可能地最大化GPA
if any of them had a lower GPA I should kick them out,

那么如果有人的GPA略低他会被排除
and if one of them has a higher GPA than the other two,

如果有一个人的GPA是最高的
I should kick out both the other two.

我当然要排出那两个人
So if I'm including all three of them,

如果他们三个人都被选中
in my constructing of the average all of them must have the same GPA,

这说明他们的GPA是相同的
which I'm going to assume is 3.9,

即我刚才假设的都是3.9