作者wwpp (wwpp)
看板GMAT
标题[问题] OG里的问题
时间Sat Feb 23 20:36:51 2008
再OG里有一题题目是
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 household that used both brands of soap,
3 used only Brand B soap.
How many of the 200 households surveyed used both brands of soap?
由於解答里写的是仅用B的是AB都用的三倍?
请问这可以从哪里看是三"倍"，而不是三个
谢谢
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