Russell calls MC’s Used Car Dealership and tells him what kind of car he is looking for.MC says,“Come down tomorrow and we will have some cars to show you.” When Russell shows up the next day,MC says,“C’mon down.We have 12 cars ready to sho
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Russell calls MC’s Used Car Dealership and tells him what kind of car he is looking for.MC says,“Come down tomorrow and we will have some cars to show you.” When Russell shows up the next day,MC says,“C’mon down.We have 12 cars ready to sho
Russell calls MC’s Used Car Dealership and tells him what kind of car he is looking for.MC says,“Come down tomorrow and we will have some cars to show you.” When Russell shows up the next day,MC says,“C’mon down.We have 12 cars ready to show you.” Of the 12 cars,there are 6 Hondas and 6 BMWs.For each make of car,there is one from each year from 2002 to 2007.Assuming MC shows Russell the cars one at a time and in no particular order,what is the probability that the first three cars he looks at are in descending model years?Round your answer to the nearest thousandth.
Russell calls MC’s Used Car Dealership and tells him what kind of car he is looking for.MC says,“Come down tomorrow and we will have some cars to show you.” When Russell shows up the next day,MC says,“C’mon down.We have 12 cars ready to sho
其实数学的应用题都能简化成一个数学模型,也许我把中间的英文翻译给跳了,引用一下“onlylm_n”的话,有一个叫Russell的要买车.卖车的人MC说：明天来,我会给你看一些车.第二天,Russell来了,卖车的人给他看了12辆车.其中有6辆本田,6辆宝马.两种车的生产年份分别是从2002到2007.MC每次给他看一辆车,没有任何顺序.问：有多少的机会他所看到的前三辆车是按年份降续排列的?
所以简化成我们刚学概率的模型,就是,有红蓝2种球,各有6个,分别标号1-6,依次抽取3个球,其号码是降续排列的概率是多少（不分颜色）?
分母是12X11X10,分子有点麻烦,可以分成几种情况用加法原理：
1 纯色球.2X(6X5X4)/(3X2X1),就是6个球拿3个球的组合,因为只有一种排列是合法的,所以用组合数公式
2 有一个红球（和有一个篮球是一样的）.2X6X(5X4)/(2X1).第一步取一个球,第二步在另一种颜色中取号码不同的另两个球,就是在5个球中取2个球的组合,因为只有一种排列是合法的,所以也是用组合数公式.
所以我的答案是4/33.
不是吧?