求助~~~请童鞋们帮解答输血JJ里的一道prep原题~为什么选A呢？

宝贝菜菜0804

Last month 15 homes were sold in Town X. The arithmetic mean sale price of the homes is $150,000 and the median 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 oe of the homes was sold for less than $130,000.

Answer choices
I only
II only
III only
I and II
I and III

答案：A

tracyw700

median为130，000代表前八个数都小于等于130,000.后面七个都大于等于130,000
第一个结论： 如果前八个数都等于130，000,那么后面七个数的和是为1，210,000。如果后面七个数都小于165,000，那么这七个数的和为1，155，000.小于1,210,000.所以，后面七个数至少有一个大于165,000
所以正确
第二个结论：如果前八个数都为130,000，后面七个数也都等于172,857，那么没有一个满足大于130,000.小于150，000的情况，所以错误
第三个结论：参照第二个结论的思路，错误

宝贝菜菜0804

哦！NN~经过提点顿时觉悟了！哈哈~多谢啦~