再请教GWD#29的一道题，急！！

yazhouwu · 发表于 2011-8-23 00:43:04

Q9:
A total of 100 customers purchased books at a certain bookstore last week.If these customers purchased a total of 200 books, how many of the customers purchased only 1 book each?
(1)None of the customers purchased more than 3 books.
(2)20 of the customers purchased only 2 books each.

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.

答案选C，我选E
我才选C是假设所有客户至少买一本书了。。但是我的理解是不能排除部分客户一本书都不买，于是：
假设a个客户不买，b个客户买1本，c个客户买2本，d个客户买3本：
a+b+c+d = 100
a*0 + b*1 + c*2 + d*3 = 200
c = 20
因此无法求解，选E

大家觉得呢？谢谢！

sirenfish · 发表于 2011-8-23 00:50:50

1）不充分
2）不充分

A total of 100 customers purchased books，这100个人都买了书的噢。

由2得还有80个人要买下剩下的（200-40）本书，再联1，设买1本书的人为a，三本书的人为b，则a+b=80，a+3b=160得a=40，b=40
所以选C

tinyhuhu · 发表于 2011-8-23 00:54:00

同意楼上：A total of 100 customers purchased books，这100个人都买了书的噢。

yazhouwu · 发表于 2011-8-23 00:54:53

哎，明白，

问题就是这句“A total of 100 customers purchased books，这100个人都买了书的噢。”

我可能钻牛角尖了。。谢谢！

再请教GWD#29的一道题，急！！

所属分类: GMAT考试

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