GWD1-2

meckychen · 发表于 2009-12-28 13:28:14

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 The answer is C how to calculate?

meckychen · 发表于 2009-12-28 16:23:46

Anderuth · 发表于 2009-12-28 16:42:56

这样看，这个乘客从3个车子中挑一个车子，挑3次，共有27种组合，第一次挑一个车子3，第二次挑不同的车子2，第三次挑剩下的，共有6种组合，一除得到C

meckychen · 发表于 2009-12-28 17:44:21

thank you

GWD1-2

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