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GWD24 03米有问过的~

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发表于 2010-8-7 11:33:46 | 只看该作者 回帖奖励 |倒序浏览 |阅读模式
3  in a certain game played with red chips and blue chips, each red chip has a point value of X and each blue chip has a point value of Y, where X>Y and X and Y are positive integers. If a player has 5 red chips and 3 blue chips, what is the average (arithmetic mean ) point value of the 8 chips that the player has?

(1)    The average point value of one red chip and one blue chip is 5.

(2)    The average point value of the 8 chips that the player has is an integer.

答案是C,但是我觉得该选E啊~~
思路入下:

求的是(5X+3Y)/(X+Y)

条件1:知道了x+y=10,把上式化简得到并带入前式 3+(2X)/10。得不出。然后由X>Y得 X可以是6,7,8,9  ;Y与之对应的是4,3,2,1。那就有4个答案

条件2:八个数的平均数是整数,也得不出来

条件1+2:我觉得也不能得到答案。把X=6,7,8,9一个个带到3+(2X)/10里面,得不到整数滴~~

望指教!!
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