GWD10-2

[vivid]

A certain roller coaster has 3 cars, and a passenger is equally likely to ride in any one of the 3 cars each time that passenger rides the roller coaster. If a certain passenger is to ride the roller coaster three 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

answer c

[homaru]

roller coaster雲霄飛車

3!/3[sup]3[/sup]
=6/27=2/9

[JS]

just in case someone does not understand the above equation, the following is a easier approach to this question.

if u want to get into all of the 3 trains in 3 rides.
the 1st ride- there is a 3/3 choice for every train
the 2nd ride- there is only 2/3 for the remaining two trains
and the last ride u only have 1/3 train left to take

so the probability is therefore

3/3 x 2/3 x 1/3 = 2/9

[凱薩琳]

還是不懂耶...