不理解。。。

飞行2010

148.Amy's grade was the 90th percent of the 80 grades for her class.Of the 100 grades from another class, 19 were higher than Amy's, and the rest were lower.If no other grade was the same as Amy's grade, then Amy's grade was what percent of the grades of the two classes combined?

(A) 72nd

(B) 80th

(C) 81st

(D) 85th

(E) 92nd
整个题目都理解混乱，麻烦大家帮我梳理一下吧，谢谢。

jeannefq

个人理解的意思哦：
amy的成绩在她自己班的80个人里呢，她排前10%，所以她应该是第八名。（90th percent说的应该就是有多少人比她低的意思，就像GMAT分数那个比例一样）
在另外一个班里呢，只有19个人比她高
所以两个班合在一起么，大概就是第27个人，所以就是1-27/180=85%

飞行2010

恩，谢谢指导。