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If list S contains nine distinct integers, at least one of w

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If list S contains nine distinct integers, at least one of w [#permalink]

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If list S contains nine distinct integers, at least one of which is negative, is the median of the integers in list S positive?

(1) The product of the nine integers in list S is equal to the median of list S.

(2) The sum of all nine integers in list S is equal to the median of list S.
[Reveal] Spoiler: OA

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Re: If list S contains nine distinct integers, at least one of w [#permalink]

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Rock750 wrote:
If list S contains nine distinct integers, at least one of which is negative, is the median of the integers in list S positive?

(1) The product of the nine integers in list S is equal to the median of list S.

(2) The sum of all nine integers in list S is equal to the median of list S.


Let the set of 9 distinct integers in increasing order be\(a_1\) , \(a_2\) ... \(a_9\).

From F.S 1, we know that \(a_1*a_2*....a_4*a_5....a_9\) = \(a_5\) \(\to\) \(a_5(a_1*a_2*...a_4....a_9-1)\) = 0.

Thus, either \(a_5\) = 0 OR \((a_1*a_2*...*a_5....a_9-1)\) = 0, the latter is not possible as no product of 8 distinct integers can ever equal 1.

Thus, the median,\(a_5\) = 0 and not positive. Sufficient.

From F. S 2, for -4,-3,-2,-1,0,1,2,3,4,the median is 0 and a NO for the question stem. Again, for the series -10,-3,-1,0,1,2,3,4,5, the median is 1, which is positive, and hence a YES for the question stem. Thus, Insufficient.

A.
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Re: If list S contains nine distinct integers, at least one of w [#permalink]

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New post 24 Jun 2013, 14:05
mau5 wrote:
Rock750 wrote:
If list S contains nine distinct integers, at least one of which is negative, is the median of the integers in list S positive?

(1) The product of the nine integers in list S is equal to the median of list S.

(2) The sum of all nine integers in list S is equal to the median of list S.


Let the set of 9 distinct integers be\(a_1\) , \(a_2\) ... \(a_9\).

From F.S 1, we know that \(a_1*a_2*....a_4*a_5....a_9\) = \(a_5\) \(\to\) \(a_5(a_1*a_2*...a_5....a_9-1)\) = 0.

Thus, either \(a_5\) = 0 OR \((a_1*a_2*...*a_4....a_9-1)\) = 0, the latter is not possible as no product of 8 distinct integers can ever equal 1.

Thus, the median,\(a_5\) = 0 and not positive. Sufficient.

From F. S 2, for -4,-3,-2,-1,0,1,2,3,4,the median is 0 and a NO for the question stem. Again, for the series -10,-3,-1,0,1,2,3,4,5, the median is 1, which is positive, and hence a YES for the question stem. Thus, Insufficient.

A.


How did u come up with this : \(a_1*a_2*....a_4*a_5....a_9\) = \(a_5\) \(\to\) \(a_5(a_1*a_2*...a_4....a_9-1)\) = 0. ?
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Re: If list S contains nine distinct integers, at least one of w [#permalink]

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New post 25 Jun 2013, 00:28
Rock750 wrote:

How did u come up with this : \(a_1*a_2*....a_4*a_5....a_9\) = \(a_5\) \(\to\) \(a_5(a_1*a_2*...a_4....a_9-1)\) = 0. ?



Could you elaborate on your doubt? The above equation is what is given in the Fact Statement.
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Re: If list S contains nine distinct integers, at least one of w [#permalink]

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New post 25 Jun 2013, 01:10
mau5 wrote:
Rock750 wrote:

How did u come up with this : \(a_1*a_2*....a_4*a_5....a_9\) = \(a_5\) \(\to\) \(a_5(a_1*a_2*...a_5....a_9-1)\) = 0. ?



Could you elaborate on your doubt? The above equation is what is given in the Fact Statement.


The first equation is given in the fact statement OK But what about the transition from the first to the second ?

I think u factorized by a_5 from both the two parts of the equation which must lead to the following :


\(a_1*a_2*....a_4*a_5....a_9\) = \(a_5\) \(\to\) \((a_1*a_2*...a_4....a_9)\) = 1.

Am I missing something here ?
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Re: If list S contains nine distinct integers, at least one of w [#permalink]

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New post 25 Jun 2013, 01:59
Rock750 wrote:

The first equation is given in the fact statement OK But what about the transition from the first to the second ?

I think u factorized by a_4 from both the two parts of the equation which must lead to the following :

\(a_1*a_2*....a_4*a_5....a_9\) = \(a_5\) \(\to\) \((a_1*a_2*...a_5....a_9)\) = 1.

Am I missing something here ?


Yes, we cannot cancel \(a_5\) from both sides because \(a_5\) can be zero.
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Re: If list S contains nine distinct integers, at least one of w [#permalink]

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New post 31 Oct 2013, 01:28
For statement 1)

Can we deduce that since at least 1 member of the set must be negative, that would give a no answer to the stem of the question.

Ie, since at least one member is negative, the only possible answers we could get are either are 0 or <0.

Which would give a no answer to the question.

Or is this reasoning incorrect for this exam.

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Re: If list S contains nine distinct integers, at least one of w [#permalink]

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Re: If list S contains nine distinct integers, at least one of w [#permalink]

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New post 02 Apr 2017, 00:26
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Re: If list S contains nine distinct integers, at least one of w [#permalink]

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New post 19 Apr 2017, 18:39
Rock750 wrote:
If list S contains nine distinct integers, at least one of which is negative, is the median of the integers in list S positive?

(1) The product of the nine integers in list S is equal to the median of list S.

(2) The sum of all nine integers in list S is equal to the median of list S.



Statement 1:

Two possible numbers to start with are 1 and 0. We cannot have a set of 9 numbers where product of all numbers equals the median if we use 1 (e.x --3 x -2 x -1 x 1 x 2 x 3 x4 ); however, any number times 0 is 0 so if we use 0 as a median we can simply take any product of four negative numbers and multiply them by the product of four positive numbers and then by zero to yield a number equal to the mean or vice versa the product of any four negative numbers times zero times the product of any four positive numbers equals 0 a.k.a the median

Sufficient.

Statement 2

We could have a set of numbers where 0 is the median (1,2,3,4,0,-1,-2,-3,-4) the result of which would be the media- however, we could also have --6,-4,-3,-2,-1,2,3,5,7 which would equal -1 which is also the median of that set and a negative number

Insufficient

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Re: If list S contains nine distinct integers, at least one of w [#permalink]

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New post 03 Sep 2017, 02:42
Rock750 wrote:
If list S contains nine distinct integers, at least one of which is negative, is the median of the integers in list S positive?

(1) The product of the nine integers in list S is equal to the median of list S.

(2) The sum of all nine integers in list S is equal to the median of list S.



Statement 1: Product if integers = Median
Which is true only if either all terms are 1 or ,-1 or Median is zero

Since integers are distinct so median has to be zero
Sufficient

Statement 2: set may be

(-5,-4,-3,-2,1,2,3,4,5) Or
(-5,-4,-3,-2,0,2,3,4,5)

Hence median may be 1 or zero or likewise
Not sufficient

Answer Option A
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Re: If list S contains nine distinct integers, at least one of w [#permalink]

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New post 11 Sep 2017, 02:32
Rock750 wrote:
If list S contains nine distinct integers, at least one of which is negative, is the median of the integers in list S positive?

(1) The product of the nine integers in list S is equal to the median of list S.

(2) The sum of all nine integers in list S is equal to the median of list S.


Tricky but you just to be mindful of the possibilities -9 integers- all must be different

St 1

The only way this scenario could hold true is if the median were 0

suff

St 2

You could actually have different scenarios as demonstrated below

-5,-4,-3,-2,1,2,3,4,5

-5,-4,-3,-2,-1,1,2,5,6

insuff

A

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Re: If list S contains nine distinct integers, at least one of w   [#permalink] 11 Sep 2017, 02:32
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