求解答，PREP1， 数学61

kaneroy

61、of the 60 animals on a certain farm,2/3 ar-e either pigs or cows. how many of the animals are cows?

(1) the farm has m-ore than twice as many cows as it has pigs

(2) the farm has more than 12 pigs

我的理解是，就是cow+pig是四十只，so1对，2不对。
但是答案是C。。。

谢谢！！！

CrapSociety

题干说：C+P=40
条件1：C>2P，结合C+P=40，我们能知道C>=27，P<=13
条件2：P>12
OK~

CrapSociety

我怕我说的不明白，题目要求的是C，所以两个条件单独都不行，但是两

个一结合，我们能知道P百分之百是13，所以C就知道了

kaneroy

我懂了。。。太粗心，其实是more than两倍，不是两倍。该打！！