[求助]经典的排列组合题

东岸老男人 · 发表于 2007-12-16 09:49:00

Q31:

There are 5 cars to be displayed in 5 parking spaces with all the cars facing the same direction. Of the 5 cars, 3 are red, 1 is blue, and 1 is yellow. If the cars are identical except for color, how many different display arrangements of the 5 cars are possible?

A. 20

B. 25

C. 40

D. 60

E. 125

这种有特殊元素的，需要排在一起的之类，请头脑清醒的给我指点一下思路，谢谢！

yankevi · 发表于 2007-12-16 10:22:00

请问答案是不是A？=20种？

lift1217 · 发表于 2007-12-16 10:30:00

请问有答案吗

yankevi · 发表于 2007-12-16 10:33:00

这题应该是=20：）

P5,5/P3,3=20

lift1217 · 发表于 2007-12-16 10:55:00

楼上，能解释一下吗

atc · 发表于 2007-12-16 17:26:00

先排1 is blue, and 1 is yellow，排好以后顺序也就确定啦。P51P41=20

东岸老男人 · 发表于 2007-12-17 01:21:00

感谢楼上的各位！

LuLiMei · 发表于 2007-12-17 01:26:00

can i do it by this way:

C53* C21*C11.?

sorry, it should not work

i'm wondering if there is a way to solve the problem by Cmn?

[此贴子已经被作者于2007-12-17 1:30:48编辑过]

keebleegeek · 发表于 2007-12-17 07:02:00

但是题目中所说的方向又有什么用呢？

keebleegeek · 发表于 2007-12-17 07:03:00

我觉得应该x2,选40

[求助]经典的排列组合题

[求助]经典的排列组合题

所属分类: GMAT考试

正在浏览此版块的会员 ()