请教2个概率题

alan19710811

1. 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

2. On Saturday morning, Malachi will begin a camping vacation and he will return home at the end of the first day on which it rains.  If on the first three days of the vacation the probability of rain on each day is 0.2, what is the probability that Malachi will return home at the end of the day on the following Monday?

 

A.     0.008

B.     0.128

C.     0.488

D.     0.512

E.      0.640

我概率好差，请高人指点，谢谢！

[此贴子已经被作者于2008-9-16 4:00:05编辑过]

yingzh

第一题：

每一次选一辆车，有3种可能的选择，一共选3次，就是3*3*3=27种

每次都选中不一样的车，P3^3= 6种

两者相除就是所求的概率

第二题：

理解为：Saturday-不下雨，  Sunday- 不下雨， Monday-下雨

概率：0.8*0.8*0.2=0.128

alan19710811

多谢！