OG12DT6求教

chuckwang · 发表于 2011-3-20 13:15:58

今天做OG12DT6，卡在这题上蛮长时间，题目是：A marketing firm determined that, of 200 households surveyed, 80 used neither Brand A nor Brand B soap, 60 used only Brand A soap, and for every householdthat used both brands of soap, 3 used only Brand B soap.How many of the 200 households surveyed used both brands of soap? 答案是A选项15，不过是我猜出来的，我看了后面的答案解释，有一点我理解不到：It is also given that 60 households use only Brand A and that three times as many households use Brand B exclusively as use both brands.按照字面意思，题目中只给出了在所有同时使用两种品牌soap的家庭中仅仅使用Brand B的有3个，可是答案解释中给的却是在所有同时使用两种品牌soap的家庭中，仅仅使用Brand B的是同时使用两种品牌soap的3倍，这个是如何得出来的？我死活也没想明白..

bbltxl · 发表于 2011-3-20 13:20:11

for every householdthat used both brands of soap, 3 used only Brand B soap.
这句话你理解错了。
每有一个同时用两种soap的人，就有3个只用b的

chuckwang · 发表于 2011-3-20 14:29:46

哦..怪不得，那很明显是3倍了，感谢楼上的解答，受教..

OG12DT6求教

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