PP-PS1-188求助

lyjranchel

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

(A) I only

(B) II only

(C) III only

(D) I and II

(E) I and III

Answer: A

这题好像GWD上有，但是找不到了，不知道有没有人会解呢？谢谢先！

meowlac

看错了。。真丢人。。

[此贴子已经被作者于2009-5-11 18:25:54编辑过]

lyjranchel

啊，懂了，真是不好意思，今天脑袋有点生锈。。。

lyjranchel

这题答案是A哦，只有I 是对的

我是这样想的，中位数是130000，说明前后还有7个数，平均为150000>130000 , 如果把前7个数都设成130000，那么可得8*130，000+7X=15*150，000 （X为后面七个数的平均数），可以算得这个平均数是17****的，所以至少有一个会大于17****，就大于165000了

谢谢NN帮忙解答哦，呵呵