求助prep 一道数学PS题

anchoretes

X小镇出售了15套房子。 the average sales prices was 150000$, median price was 130000$. Q: which of the following must be true??

I: at least one of the 15 house was sold for more than 165000$
II: at least one of the 15 house was sold for more than 130000$ and less than 150000$
III:at least one of the 15 house was sold for less than 130000$


I,II,III 哪个或者哪几个对？

shaoyipeng

I正确
考虑几种极限情况:
中位数以下的数都等于中位数,那中位数以上的值的就能保证最小,
那么中位数以下8个数each=130k, sum= 1040k.中位数以上7个数,sum=1210k.
那么中位数以上那7个数,平均值~=170k.已经大于165k了.那就说明肯定有比165k大的数.

II,可以从I这种情况看出来,有一种情况是中位数以下都是130k,而中位数以上的数都约等于170K.那样就得不出II了

III, non sense...

tomchengs

根据楼上的1中的假设，中位数以下都是中位数，这种情况成立，3不就错了么。

anchoretes

答案是ONLY I 正确~~~~
2L谢谢哈~~~很CLEVER~~~~感谢~~~就是这么做的。。想破脑袋才想明白···美国人智商不能低估啊。。