数学Prep题目DS请教-2 谢谢~~

ranshuyang · 发表于 2012-10-20 22:07:23

x, 3, 1, 12, 8
If x is an integer, is the median of the 5 numbers showngreater than the average (arithmetic mean) of the 5 numbers?
(1) x > 6
(2) x is greater than the median of the 5 number
各位牛牛，请问解这类题目有没有什么简单的方法？
困扰已久~~~

ranshuyang · 发表于 2012-10-20 22:16:29

是不是只能这么一个一个试呢？
把已知的数字排序
1, 3, 8, 12, ... X
median M
mean (1+3+8+12+x)/5

(1) x >6 if x=7 then M = 7 mean = 4.2
if x = 20 then M = 8 mean = 8.8 so (1) alone can't

(2) x greater than the median of the 5 number ==> x >8
if x = 9 then M =8 mean = 6.6
if x = 30 then M =8 mean = 10.8 so (2) alone can't either

(1)+(2) = (2)
so can't say weather median greater then mean.

sceaxus · 发表于 2012-10-21 08:59:47

哇噻，牛人，看了你的解释我如梦初醒，昨天就载载这里。。。不知道怎么下手

数学Prep题目DS请教-2 谢谢~~

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