请教 OG11-yellow黄皮21页-第6题

auroral1982 · 发表于 2009-4-15 13:58:00

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?

(A) 15
(B) 20
(C) 30
(D) 40
(E) 45

标准答案是A。我明白这道题比较简单，但是对于这句话：“and for every household that used both brands of soap, 3 used only Brand B soap.” 着实是按着答案来理解的一个"比例提示"。

想请教一下大家，这样的说法对吗？在GMAT的考试中、复习准备中常见吗？

本人刚刚开始准备GMAT，更是6年没有碰过数学了。。。多谢各位大侠的不吝赐教！

请教 OG11-yellow黄皮21页-第6题

请教 OG11-yellow黄皮21页-第6题

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