PREP 模考中碰到几个困惑的题，希望大家帮忙看看

馒头emerald

1. of the 60 animals on a certain farm, 2/3 are either pigs or cows. How many of the animals are cows?
1) The farm has more than twice as many cows as it has pigs
2) The farm has more than 12 pigs


2. Three grades of milk are 1 percent, 2 percnet, 3percent fat by volume. If x gallons of the 1 percent grade, y gallons of 2 percent grade, and Z gallons of the 3 percent grade are mixed to give x+y+z gallons of a 1.5 percent grade, what is X in terms of y and z ?

A) y+3z   B) (y+z)/4    C) 2y+3z  D)3y+z   E) 3y+4z

3. X, 3,1,12,18   If X is an integer, is the median of the 5 numbers show greater than the average(arithmatic mean) of the 5 number?
1) X>6   
2) X is greater than the median of then 5 number

这道题我能用自己的笨方法做出来，但是会浪费很多时间，想求教各位的做题方法。

希望各位有解题思路的能帮帮我，不胜感激！！  

francoisyang

1. 40头猪和牛，条件1牛比猪多2倍以上，条件2猪超过12头，2个条件如果结合，唯一可能性就是13头猪，27头牛；
2. 1%x+2%y+3%z=1.5%(x+y+z)，x=y+3z
3. 3<=median<=12,average=(34+X)/5,然后分段考虑。

馒头emerald

francoisyang 发表于 2013-6-17 17:47
1. 40头猪和牛，条件1牛比猪多2倍以上，条件2猪超过12头，2个条件如果结合，唯一可能性就是13头猪，27头牛 ...

太感谢啦。。。