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标题: 我的理解是不是哪里有误？ [打印本页]

作者: shirleymin0717 时间: 2017-11-10 15:53
标题: 我的理解是不是哪里有误？
Last month 15 homes were sold in Town X. The average (arithmetic mean) sale price of the homes was $150,000 and the median sale price was $130,000. Which of the following statements 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.

AI only
BII only
CIII only
DI and II
EI and III

正确答案: A
第三个为什么不对啊？median是130，000，那肯定至少有一个是比它小啊？我是哪里被绕进去了吗？

作者: qx24601 时间: 2017-11-10 16:14
可以有8个都是130000啊，只要剩下的数都足够大

作者: 羽宝儿 时间: 2017-11-10 16:19
I的那个数字165000怎么的出来呀. II和III都明白错了。可是这个165000这个数字怎么得出来的，楼主知道吗~

作者: shirleymin0717 时间: 2017-11-11 08:11
谢谢，忘记了前8个数可以都等于median。

当前面7个都为最大130，第8个median也是130，130*8=1040，然后后面7个最小值，后7个数的平均值为：（15*150-1040）/7=172.85。也就是说后7个数取最小时平均值为172.85，则得出必然有一个数大于165.

以上数值均少算1000，以便计算简单。

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