GWD数学~~~

bobchowz

Town T has 20,000 residents, 60 percent of whom are female. What percent of the residents were born in Town T?

(1) The number of female residents who were born in Town T is twice the number of male residents who were not born in Town T.

(2) The number of female residents who were not boen in Town T is twice the number of female residents who were born in Town T

答案是B。
求NN分析下~~~~

shlshingse

第2个条件没有提到male怎么能确定所有居民的比例呢。答案错了。选C。

bobchowz

我也深深觉得是C。。。谢谢了.

EthanEthan

简单设：没生在T的，FNBT，MNBT，生在t的，FBT，MBT好吧~~
结合题干已知：条件一：fnbt+fbt=12000
                                      mbt+mnbt=8000
                                      fbt=2mnbt              

  三个方程四个未知数，不行吧
                         条件二：同理三个方程四个未知数，还

是不行
     条件一+条件二刚好，四个方程四个未知数，可解~~