Gmat Prep question 3

[msd_2008]

Q. 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 are it has pigs

2. The farm has more than 12 pigs

[pepeprepa]

1. The farm has more than twice as many cows are it has pigs
2. The farm has more than 12 pigs

With 1 and 2 alone we cannot find anything.

1 and 2

Here is what we know:
(2/3)*60=P+C
40=P+C

C>2P
P>12

We see the only possibility is P=13, then C=27 because P+C=40
We have 13>12 and 27>2*13 which are respected.

If you choose P=14; C=26 so as to get 14+26=40 but 26<2*14 so it's wrong.