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标题: 请教4道GWD 的数学题(已解决) [打印本页]

作者: laijiaqoo    时间: 2010-3-23 21:04
标题: 请教4道GWD 的数学题(已解决)
GWD-1

Q9:

A gardener is going to plant 2 red rosebushes and 2 white rosebushes.If the gardener is to select each of the bushes at random, one at a time, and plant them in a row, what is the probability that the 2 rosebushes in the middle of the row will be the red rosebushes?



A.1/12

B.1/6

C.1/5

D.1/3

E.1/2

Answer: B



Q26:

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

Answer: E





Q28:

For any positive integer n, the sum of the first n positive integers equals [n(n+1)]/2.What is the sum of all the even integers between 99 and 301?



A.10,100

B.20,200

C.22,650

D.40,200

E.45,150

Answer: B





Q30:

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.

Answer: D





作者: 意米    时间: 2010-3-24 12:30
第一,分母四个全排列,A44;分子,白花只排两边有两种,红花在中间自己内部排一下两种2*2/A44
作者: annedx    时间: 2010-3-24 15:44
Q30错了吧,应该是C
作者: laijiaqoo    时间: 2010-3-24 19:46
额..Q30 我觉得第二个单独是可以的.  只是不知道第一个怎么可以.
作者: laijiaqoo    时间: 2010-3-24 19:47
谢谢 的确是这样子.
作者: laijiaqoo    时间: 2010-3-24 19:50
额..Q30 我觉得第二个单独是可以的.  只是不知道第一个怎么可以.
-- by 会员 laijiaqoo (2010/3/24 19:46:57)


喔  我看错了 的确第二个单独是不可以




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