Prep-PS-148

oceanfish

148.        15080-!-item-!-187;#058&010499
Amy's grade was the 90th percentile 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 percentile of the grades of the two classes combined?

(A) 72nd
(B) 80th
(C) 81st
(D) 85th
(E) 92nd

BeyondY

80个人里有8个比他高,那100里有19个比他高,没有跟他一样的,一共27个比他高,180个人,所以他的成绩是1-27/180=85%

chili

求出分比Amy高的人数，再除以总人数，得出Amy的排名。

apricot

这题的百分数跟GMAT成绩单的 percentile是同样的意思，Amy’s grade在80个人中排第八名（80*0.1），所以则有7个人比她分数高，72个人比她分数低；第二个条件里有19个人比她高，80个人比她低；两个结果综合一起，在这179个人中，一共有26个人分数比她高，所以她排名为27,答案就是=（1-27/179）*100%=85th