作者fly12404 (郭品超)
看板GMAT
标题Re: [计量] gwd 29-9
时间Sun Aug 17 19:03:26 2008
※ 引述《dolphin100 (得分100~~YA)》之铭言：
: 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.
: 答案是C ，可是我觉得很怪，搞不懂
买1本 x 人 , 买2本 y人 买3本 z人
1)没人买超过三本 => x + y +z =100 x+2y+3z=200
不充分
2)20人买二本
不充分
1+2) y = 20
x +z = 80
x + 40 +3z = 200
可以求出只买一本的
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1F：推 dolphin100:谢谢^^ 08/18 15:29