新手启程，很弱地问OG12中的数学 sample questions

bowow

数学的。。。

第六题

 a maketing 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 household surveyed used both brands of soap?

a:15   b:20 c:30 d:40 e:50

答案是a：15.

看了解释：since it is given that 80 household use neither brand a nor brand b, then 200-80=120must use brand a, brand b, or both. it is also given that 60household use only brand a and that  3 times as many household use brand b exclusively as use both brands.

问题出来了。。。我看提干中看不出3times。。。。莫非是打印出错。。。汗。。。还是我太弱了。。。 

terrjtly

红字部分的后半句就是3times的来源

aquarius_wei

我也是个新手说。。。同问。。。

icefire9981

其实这个题的关键就是这句话 for every household that used both brands of soap, 3 used only brand b soap

这句话可以这么理解：对于每一个both，都有3个brand b来对应，也就是说b是both的3倍。

bowow

谢谢各位大侠帮助！～记住这个表达方式了！～