刚上手，请问一下GWD math1 q2怎么解呢。。。

xyc19901015 · 发表于 2011-2-7 23:44:36

Q2:
A certain roller coaster has 3 cars, and a passenger is equally likely to ride in any 1 of the 3 cars each time that passenger rides the roller coaster. If a certain passenger is to ride the roller coaster 3 times, what is the probability that the passenger will ride in each of the 3 cars?

A.   0
B.   1/9
C.   2/9
D.   1/3
E.   1
答案选2/9，费解中。。。高中学的都忘了，我咋觉得是1/9类。。。感谢大侠指点！

Jingfei · 发表于 2011-2-8 01:38:32

3*2/3^3=6/27=2/9

kazemi · 发表于 2011-2-8 01:54:57

Choosing the first car is irrelevant.

Second time we have 2 choices.

Third time we only have 1 choice.

1*2/3*1/3 = 2/9

or the other method is

you have 3 cars ABC

ABC can be arranged in 3! ways or 6 ways.

Total permutations = 3*3*3 = 27

Probability = 6/27 = 2/9

Hope this helps.

xyc19901015 · 发表于 2011-2-8 16:02:57

感谢感谢！

刚上手，请问一下GWD math1 q2怎么解呢。。。

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