标题: prep的一道题 [打印本页]
作者: mvmv90 时间: 2010-3-17 07:29 标题: prep的一道题
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.
此题我怎么都想不通为什么只用第二个条件就可以算出答案
patio no-patio
pool a b
no-pool c a
48 27(75-48)
以上就是单靠第二个条件所能得出的信息，how could it get the answer directly...???
作者: tonger 时间: 2010-3-17 20:14
LZ画个图吧，就是那种两个圈圈相交的图...
然后你就会惊讶地发现，只有游泳池而没有露台的人数，加上两个都有的人数，就等于拥有游泳池的人数,,,而两个都有的，等于两个都没有的...而两个都没有的加上只有游泳池的，就是75-48...
作者: mvmv90 时间: 2010-3-18 06:56
感谢LS！顺便想问一下为什么我那种方法算不出结果呢？我一直以为那种方法万能的...
thx again
作者: jiuwang 时间: 2010-3-21 09:39
just use your information:
a + b + a + c = 75 (total house)
a + c = 48 (house with patio)
question: a + b = ? (house with pool)
作者: mvmv90 时间: 2010-3-21 19:36
right...got u...thx u, both of u, so much indeed
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