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crystalhearts 发表于 2010-2-11 18:08

请教数学题

Of the 75 houses in a certain community, 48 have a patio. How many of the houses in the community have a swimming pool?

(1) 38 of the houses in the community have a patio but do not have a swimming pool
(2) The number of houses in the community that have a patio and a swimming pool is equal to the number of houses in the community that have neither a swimming pool nor a patio

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

PrepTest 上的答案是B， 请问为什么。。。？

JJJooe 发表于 2010-2-11 21:20

单独条件1很明显不成立
因为pool和patio都没的数量未知

单独条件2时
都有和都没有的数量一样
你干脆就设成x好了
再设我们要求的有pool的为y

那么y+48-x+x=75(这个看得懂吧)
恰好x都被消掉了于是y=75-48=27

crystalhearts 发表于 2010-2-11 23:48

对噢！！谢谢！！！！

对噢！！谢谢！！！！

sasa0914 发表于 2010-3-8 22:18

条件1是成立的，2不成立。所以答案是B。

条件1：38have a patio,48中10个既有patio又有swimming pool。 用总数75-48=27，就是由游泳池的数量。
条件2则缺少信息。

JJJooe 发表于 2010-3-9 09:40

回复 4# sasa0914 的帖子

解释是对的..但是说反了==

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