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gmat prep question

by yvonne12 » Tue Apr 10, 2007 3:33 pm
Of the 60 animals on a certain farm, 2/3 are either pigs or cows. How many of the animals are cows?

I. The farm has more than twice as many cows as it has pigs

II. the firm has mroe than 12 pigs

I thought it was I since 60(2/3)=40 and p=2c and p+c=40 sp, 2c +c =40, c=13 and you can get your answer that way, but the answer is c. why??
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Re: gmat prep question

by gabriel » Tue Apr 10, 2007 10:44 pm
yvonne12 wrote:Of the 60 animals on a certain farm, 2/3 are either pigs or cows. How many of the animals are cows?

I. The farm has more than twice as many cows as it has pigs

II. the firm has mroe than 12 pigs

I thought it was I since 60(2/3)=40 and p=2c and p+c=40 sp, 2c +c =40, c=13 and you can get your answer that way, but the answer is c. why??

the number of cows of pigs are 40....


now according to the first statement the no. of cows is more than twice the number of the pigs.. that is if the number of pigs is p then the number of cows is > 2p.. now no. of cows + no. of pigs = 40 ... 2p+p<40 ( we get this bcoz we are not adding the exact number of cows .... but a number less than it... bcoz the number of cows is > 2p) .. so p < 13.333 ... does not give a definite answer so insufficient ..


the 2nd statement says that p>12.. which again does not giv a definite answer .. so insufficient

combine the two and u get p < 13.33 and p >12 and the only intger value that satisfies this condition is 13 so p=13 .. and the no. of cows is 40-13=27 .. so C is the answer...
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yes

by yvonne12 » Wed Apr 11, 2007 4:14 pm
yes! I understand. I need to read more carefully "to more than twice " not "twice than"
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by Cybermusings » Thu Apr 12, 2007 7:45 am
Of the 60 animals on a certain farm, 2/3 are either pigs or cows. How many of the animals are cows?

I. The farm has more than twice as many cows as it has pigs

II. the firm has mroe than 12 pigs

Statement I- 2/3 either pigs or cows. Thus the remainder i.e. 1/3 are neither cows nor pigs (1/3*60) = 20
So cows + pigs = 60-20 = 40
Now if pigs are x, cows = >2x
This statement alone is insufficient

Statement II
Firm has more than 12 pigs. All we know is that cow and pigs are 40 and out of these pigs are more than 12. This is insufficient

Both together
x + y = 40
x>12
y>2x (where y is the number of cows)
If pigs are 13, cows would be 27, which is more than twice the number of pigs
If pigs are 14, cows would be 26, which is less than twice the number of pigs. This violates the statements

Hence Answer is C. Two statements together are correct but neither one alone
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by gabriel » Thu Apr 12, 2007 7:52 am
Cybermusings wrote:Of the 60 animals on a certain farm, 2/3 are either pigs or cows. How many of the animals are cows?

I. The farm has more than twice as many cows as it has pigs

II. the firm has mroe than 12 pigs

Statement I- 2/3 either pigs or cows. Thus the remainder i.e. 1/3 are neither cows nor pigs (1/3*60) = 20
So cows + pigs = 60-20 = 40
Now if pigs are x, cows = >2x
This statement alone is insufficient

Statement II
Firm has more than 12 pigs. All we know is that cow and pigs are 40 and out of these pigs are more than 12. This is insufficient

Both together
x + y = 40
x>12
y>2x (where y is the number of cows)
If pigs are 13, cows would be 27, which is more than twice the number of pigs
If pigs are 14, cows would be 26, which is less than twice the number of pigs. This violates the statements

Hence Answer is C. Two statements together are correct but neither one alone

...nice detailed explanation...
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