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
网上的答案选Ｃ，为什么？
Q2:
Running at their respective constant rates, machine X takes 2 days longer to produce w widgets than machine Y.At these rates, if the two machines together produce 5/4 w widgets in 3 days, how many days would it take machine X alone to produce 2w widgets?
A.4
B.6
C.8
D.10
E.12
为什么答案为Ｅ
Q3:
Joanna bought only $0.15 stamps and $0.29 stamps.How many $0.15 stamps did she buy?
(1)She bought $4.40 worth of stamps.
(2)She bought an equal number of $0.15 stamps and $0.29 stamps.
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.
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发表于 2009-8-10 01:27:00
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