请教两道PREP数学~

cat411 · 发表于 2009-12-28 17:17:16

DS:If X and Y are positive integers, is XY a multiple of 8?

(1)The greatest common divisor of X and Y is 10

(2)The least common multiple of X and Y is 100

PS: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. If no other grade was the same as Amy's.The Amy's grade was what percentile of the grades of the two classroom combined?

Anderuth · 发表于 2009-12-28 17:23:48

第一题选b，1这个条件有可能x和y都是10，那么xy就不是8的倍数了。

第二题，第一个班比amy分数高的有7个，第二个班比amy高的有19，两个班加起来有26个，两个班总人数是180，所以amy就是1－27/180＝85th percentile

cat411 · 发表于 2009-12-28 17:31:24

第一题答案给的是C来着。。。
啊。。。第二题我搞反了，我以为was the 90th percentile 是倒数10%的意思来着。。。

谢谢楼上的~~

请教两道PREP数学~

所属分类: GMAT考试

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