Data Sufficiency

of the 60 animals on the farm, 2/3 are either pigs or cows. how many of the animals are cows?

a) the farm has more than twice as many cows as it has pigs
b) the farm has more than 12 pigs

Ans C

What I don't understand here is the phrase - 2/3 are either pigs or cows

My understanding from this was that it is
either
20 Cows and 40 pigs
or
40 cows and 20 pigs.

Could you please explain here?

smayekar wrote:What I don't understand here is the phrase - 2/3 are either pigs or cows

My understanding from this was that it is
either
20 Cows and 40 pigs
or
40 cows and 20 pigs.

Could you please explain here?

Let's read the first part of the sentence:

"Of the 60 animals on the farm, 2/3 are..."

No matter what comes next, we know that it's describing 2/3 of the animals on the farm. For example, if the next words were "dogs", we'd immediately think "there are 40 dogs on the farm"; if the next words were "penguins", we'd immediately think "there are 40 penguins on the farm" (and "wow, I want to visit that farm!").

So, just because the next phrase is more complicated than "dogs" or "penguins", it doesn't change how we interpret the sentence. When we see "either pigs or cows", we should immediately think that 40 of the animals on the farm are either pigs or cows.

Accordingly, we know that cows + pigs = 40.

The question: how many cows are on the farm?

On to the statements!

(1) there are more than twice as many cows as pigs. No need for lots of math - could be 39 cows and 1 pig or 38 cows and 2 pigs: insufficient, eliminate A and D.

(2) more than 12 pigs. No need for lots of math - could be 13 pigs and 27 cows or 27 pigs and 13 cows: insufficient, eliminate B.

Combined:

more than 12 pigs means at least 13 pigs. If we have 13 pigs, we'd have 27 cows - that's legal accordingly to (1). If we have 14 pigs, we'd have 26 cows - that violates (1). Add more pigs and we decrease the cows, further violating (1). Accordingly, there must be 13 pigs and 27 cows: sufficient, choose (C).