数学题

superjeanjean · 发表于 2012-10-7 17:24:07

OG13 第6题题目是不是有问题?
要怎么做...

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?
答案是A 15

谢谢><!!!

Mandy2010 · 发表于 2012-10-7 17:35:08

划线部分没读懂吧，意思是说，对应两个都用的，有三倍的人会用B，然后就简单了，设a，b，c，a=60，3c=b，a+b+c=200-80，就ok了

superjeanjean · 发表于 2012-10-7 17:37:42

喔原来是三倍的意思！！明白了！！
谢谢~~~

Mandy2010 · 发表于 2012-10-7 21:52:11

不谢不谢哈

数学题

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