一道想不通的prep数学。。。大家帮忙看看看看呀~~{已解决}

小蛋黄 · 发表于 2010-7-20 18:20:00

last month 15home were sold in town X, the average sale price was 150,000 and the medien sale price was 130,000. which of the following statement must be true?

I. at least one of the homes was sold for more than 165,000
II. at least one of the homes was sold for more than 130,000 and less than 150,000.
III. at least one of the homes was sold for less than 130,000

答案说只有I 是对的。。。但是我觉得III也正确呀。。。而且不明白为什么I是对的呢？ 165,000哪里来的呀？

Nickyl86 · 发表于 2010-7-20 19:18:06

III错的，有种可能是14所房子都卖130K，只有一所卖到超高价，平均价还是150K

Nickyl86 · 发表于 2010-7-20 19:27:37

再来说说为啥1是对的，已知中位数十130K，这样的话，我们假设房价按从小到大排列，前8所房子都卖130K，那剩下来7所房子的平均价为（150K*15-130K*8）/7=170+K，这7所平均数就抄165K了，那肯定有一所要超过165K

如果前8所房子里面有一所卖价低于130K，那剩下7所的平均价格会更高，所以I肯定正确的

小蛋黄 · 发表于 2010-7-20 20:01:54

恩恩，解释的真清楚！！！ O(∩_∩)O谢谢

Nickyl86 · 发表于 2010-7-20 20:12:27

表客气，不过lz可以把标题写成“已解决”了

一道想不通的prep数学。。。大家帮忙看看看看呀~~{已解决}

所属分类: GMAT考试

正在浏览此版块的会员 ()

浏览过的版块