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M02-18

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Re: M02-18  [#permalink]

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New post 13 Feb 2018, 05:25
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New post 13 Feb 2018, 05:55
Bunuel wrote:
karn99 wrote:
I think this is a poor-quality question and the explanation isn't clear enough, please elaborate.


I'd suggest to read the whole discussion once again and ask specific question.

P.S. The question is 100% correct and up to highest GMAT standards. It's not that easy though for novices.


According to statement (2) the set S can contain {-1,2,-3} and isn't it sufficient to answer that all the elements of set S are NOT negative?
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New post 13 Feb 2018, 05:58
karn99 wrote:
Bunuel wrote:
karn99 wrote:
I think this is a poor-quality question and the explanation isn't clear enough, please elaborate.


I'd suggest to read the whole discussion once again and ask specific question.

P.S. The question is 100% correct and up to highest GMAT standards. It's not that easy though for novices.


According to statement (2) the set S can contain {-1,2,-3} and isn't it sufficient to answer that all the elements of set S are NOT negative?


(2) The product of the smallest and largest integers in the set is a prime number.

In set {-1,2,-3} the smallest number is -3 and the largest number is 2, their product is -6, which is not a prime number.
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New post 13 Feb 2018, 09:34
As the questions says that the product of any three numbers is negative.

Lets say if one number is positive,
+1, -1, -3, -9

As it says any three integers, we can take +1, -1, -3
prod = +3

The only way the product of "ANY" three integers are negative is only if all the numbers in the set are -ve.

The answer should be A.
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M02-18  [#permalink]

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New post 07 Jul 2018, 04:33
Hi Bunuel!

This question was in my Quant CAT today. I chose A. At the back of my mind, I was confused between A and C. But could not find a good an example. In the question it says that set S has more than 2 integers and according to statement 1, product of any 3 integers is negative. The explanation gives an example where S has 3 integers. Consider the following set
{2,3,-5,-2,-4}
In this set, the product of any 3 integers will be negative if we take odd number of negative integers i.e 1 and 3. However, in a case where we choose {2,-5,-4} or similar 3 integers from set S, where there are even number of negative integers, the product is positive.
Please can you help me identify my mistake.

Thanks,
V
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New post 07 Jul 2018, 08:19
vaibhav1221 wrote:
Hi Bunuel!

This question was in my Quant CAT today. I chose A. At the back of my mind, I was confused between A and C. But could not find a good an example. In the question it says that set S has more than 2 integers and according to statement 1, product of any 3 integers is negative. The explanation gives an example where S has 3 integers. Consider the following set
{2,3,-5,-2,-4}
In this set, the product of any 3 integers will be negative if we take odd number of negative integers i.e 1 and 3. However, in a case where we choose {2,-5,-4} or similar 3 integers from set S, where there are even number of negative integers, the product is positive.
Please can you help me identify my mistake.

Thanks,
V


{2,3,-5,-2,-4} does not satisfy the condition that the product of ANY three integers in the set is negative: 2*(-5)*(-2) = 20 = positive.

As explained in the solution, this could be true if:
a. the set consists of only 3 terms, then the set could be either {negative, negative, negative} or {negative, positive, positive}.
b. the set consists of more than 3 terms, then the set can only have negative numbers.
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New post 18 May 2019, 15:14
Question is not of great quality, i can't imagine finding this question on GMAT exam.

1. Have to remember that primes are only positive - Kind of never tested quality of Primes.
2. Have to remember that one of the two cases in statement 1 was (-,+,+) and use the fact that the product of the lowest and highest number is a prime, hence positive.
Therefore case of (-,+,+) is not possible. Its a stretch.

If it was given that the product of the lowest and greatest is positive then, we are getting closer to a real GMAT Q.
I suspect that positive was changed to prime to make it more difficult, which just doesn't work somehow.
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New post 22 Sep 2019, 23:54
I think this is a high-quality question and I agree with explanation.
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Re M02-18   [#permalink] 22 Sep 2019, 23:54

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