请教！GWD

martycai · 发表于 2010-6-2 12:30:20

Theater M has 25 rows with 27 seats in each row. How many of the seats were occupied during a certain show?

(1) During the show, there was an average (arithmetic mean) of 10 unoccupied seats per row for the front 20 rows.

(2) During the show, there was an average (arithmetic mean) of 20 unoccupied seats per row for the back 15 rows.

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.

答案是E，什么思路啊？

terrybaroque · 发表于 2010-6-3 03:47:44

思路是先设一个未知量即前20排和后15排中间重叠10排的每排被占座位的平均数为X 联立条件1和2 于是我们有整个剧院的被占座位的总数为 20*（27-10）+15*（27-20）- 10*X ，显然 X没有具体提及条件1和2联立不充分选E

lcj2003kit · 发表于 2010-6-3 11:06:09

根据1和2可以单独推算出被占的座位数
但是1和2一起就不行。。。。
前20排每排空10个和后15排每排空20个矛盾，一共只有25排，那中间10到20排该空几个喃？
我觉得是这样的哈。。。。

请教！GWD

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