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  M24 Q 33 [#permalink]
PostPosted: Thu Mar 12, 2009 2:59 pm 
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If sets S and T are united into a single set, will the mean of this set be smaller than the sum of means of sets S and T ?

1. S and T are one-element sets
2. Neither set S nor set T contains negative numbers

[Reveal] Spoiler: OA
E

Source: GMAT Club Tests - hardest GMAT questions

I will let you guys discuss this. How ever, The two Set opeartions I remember are union and intersection. How are we supposed to interpret merge.

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  Re: M24 Q 33 [#permalink]
PostPosted: Thu Mar 12, 2009 7:06 pm 
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icandy wrote:
If sets S and T are merged into a single set, will the mean of this set be smaller than the sum of means of sets S and T ?

1. S and T are one-element sets
2. Neither set S nor set T contains negative numbers

(C) 2008 GMAT Club - m24#33

* Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient
* Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient
* BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient
* EACH statement ALONE is sufficient
* Statements (1) and (2) TOGETHER are NOT sufficient

I will let you guys discuss this. How ever, The two Set opeartions I remember are union and intersection. How are we supposed to interpret merge.



I believe two operations and "union" and "union all" --> if you know ORACLE sql LANGUAGE. :lol: :lol: :lol:
( I may be wrong.. but thats what I interpret.. as IT .. nerd)

e.g
A ={1,3} B={1,5}

Merge = {1,3,5} ( all distinct elements) avg = 3
Sum = {1,1,3,5} avg= 10/4 = 2.5


another e.g.
A ={1,5} B={3,5}
Merge = {1,3,5} ( all distinct elements) avg = 3
Sum = {1,3,5,5} avg= 14/4 = 3.66



I will go with E.

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  Re: M24 Q 33 [#permalink]
PostPosted: Fri Mar 27, 2009 10:47 am 
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Couldnt get this!!
It is sum of the means of A and B.
e.g
A ={1,3} B={1,5}

Merge = {1,3,5} ( all distinct elements) avg = 3
Sum = {1,1,3,5} avg= 10/4 = 2.5 >> cant understand this.

Sum of means should be 2 + 3 = 6.May be my understanding is wrong. Please explain.

x2suresh wrote:
icandy wrote:
If sets S and T are merged into a single set, will the mean of this set be smaller than the sum of means of sets S and T ?

1. S and T are one-element sets
2. Neither set S nor set T contains negative numbers

(C) 2008 GMAT Club - m24#33

* Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient
* Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient
* BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient
* EACH statement ALONE is sufficient
* Statements (1) and (2) TOGETHER are NOT sufficient

I will let you guys discuss this. How ever, The two Set opeartions I remember are union and intersection. How are we supposed to interpret merge.



I believe two operations and "union" and "union all" --> if you know ORACLE sql LANGUAGE. :lol: :lol: :lol:
( I may be wrong.. but thats what I interpret.. as IT .. nerd)

e.g
A ={1,3} B={1,5}

Merge = {1,3,5} ( all distinct elements) avg = 3
Sum = {1,1,3,5} avg= 10/4 = 2.5


another e.g.
A ={1,5} B={3,5}
Merge = {1,3,5} ( all distinct elements) avg = 3
Sum = {1,3,5,5} avg= 14/4 = 3.66



I will go with E.


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  Re: M24 Q 33 [#permalink]
PostPosted: Sun Mar 29, 2009 8:37 pm 
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icandy wrote:
If sets S and T are merged into a single set, will the mean of this set be smaller than the sum of means of sets S and T ?

1. S and T are one-element sets
2. Neither set S nor set T contains negative numbers

I will let you guys discuss this. How ever, The two Set opeartions I remember are union and intersection. How are we supposed to interpret merge.


For me merged = combined.

1: S and T are one-element sets
If S = T = 2, mean of the merged set (2, 2) = 2 and sum of the means of sets S and T is 4.
If S = 2, and T = -2, mean of the merged set (2, -2) = 0 and sum of the means of sets S and T is 0.
If S = 0, and T = 0, mean of the merged set (2, 2) = 0 and sum of the means of sets S and T is 0. NSF..

2: Neither set S nor set T contains negative numbers
If S = T = 2, mean of the merged set (2, 2) = 2 and sum of the means of sets S and T is 4.
If S = 0, and T = 0, mean of the merged set (2, 2) = 0 and sum of the means of sets S and T is 0. NSF.

Togather alos nsf.
E.

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  Re: M24 Q 33 [#permalink]
PostPosted: Sun Mar 29, 2009 9:39 pm 
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Answer should be E - not sufficient in any of the cases.
What's the OA?


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  Re: M24 Q 33 [#permalink]
PostPosted: Mon Mar 30, 2009 4:32 am 
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The OA is E.

Do you guys think we should replace "merged" with "united" in the question stem?

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  Re: M24 Q 33 [#permalink]
PostPosted: Sun Apr 05, 2009 2:59 am 
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Yes that should be better...United or union of two sets....merged is confusing :(
dzyubam wrote:
The OA is E.

Do you guys think we should replace "merged" with "united" in the question stem?


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  Re: M24 Q 33 [#permalink]
PostPosted: Thu Mar 11, 2010 7:22 am 
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Merge of sets means you need to combine.

S= {1}
T= {1,2}

Merge = {1,1,2}


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  Re: M24 Q 33 [#permalink]
PostPosted: Thu Mar 11, 2010 8:07 am 
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Both solution 1 and 2 fail the zero test.

S1: S = {0} and T = {0} => Mean of S = 0 and Mean of T = 0
Set ST = {0, 0} => Mean of ST = 0
Thus, S1 is not sufficient.

S2. Neither S nor T contain negative number.
Take the same sets: S = {0} and T = {0}
S2 is not sufficient.

Answer is E.


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  Re: M24 Q 33 [#permalink]
PostPosted: Thu Mar 11, 2010 8:35 am 
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icandy wrote:
If sets S and T are united into a single set, will the mean of this set be smaller than the sum of means of sets S and T ?

1. S and T are one-element sets
2. Neither set S nor set T contains negative numbers

[Reveal] Spoiler: OA
E

Source: GMAT Club Tests - hardest GMAT questions


s= {1,2,3}
mean1 = 2
t= {2,3,4}
mean2 = 3
sUt= {1,2,3,4}
mean3= 2.5 < mean1 + mean2

s={-1,-2,-3}
mean1 = -2
t={-2,-3,-4}
mean2 = -3
sUt= {-1,-2,-3,-4}
mean3 = -2.5 > mean1 + mean2

s={0}
mean1 = 0
t = {0}
mean2 = 0
sUt = {0}
mean3 = 0 = mean1+mean2

hence none of the two stmts solve this questions. Hence E.


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  Re: M24 Q 33 [#permalink]
PostPosted: Thu Mar 11, 2010 4:26 pm 
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vshrivastava wrote:
Both solution 1 and 2 fail the zero test.

S1: S = {0} and T = {0} => Mean of S = 0 and Mean of T = 0
Set ST = {0, 0} => Mean of ST = 0
Thus, S1 is not sufficient.

S2. Neither S nor T contain negative number.
Take the same sets: S = {0} and T = {0}
S2 is not sufficient.

Answer is E.



You only showed that you can answer the question with a definite NO.
The question being "will the mean of this set be smaller than the sum of means of sets S and T ?"

This sufficiently answers the question as a NO for both cases.

In order for the cases to be insufficient, you need to be able answer the question with both a yes and a no.

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  Re: M24 Q 33 [#permalink]
PostPosted: Sun Mar 14, 2010 2:53 am 
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friends
i understand that both options failed the zero test but why do we need a zero in set

ex- a set of 3 pen, 2 pencil and 0 flower
we can simply say it a set of 3 pen and 2 pencils, why do we consider something like zero in a set

Please explain


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  Re: M24 Q 33 [#permalink]
PostPosted: Fri Mar 19, 2010 8:18 am 
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hardnstrong wrote:
friends
i understand that both options failed the zero test but why do we need a zero in set

ex- a set of 3 pen, 2 pencil and 0 flower
we can simply say it a set of 3 pen and 2 pencils, why do we consider something like zero in a set

Please explain


Zero is considered as an entity here.
like A has 0 sets of readings 2m , 0m, 1m
so zero is the value.

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  Re: M24 Q 33 [#permalink]
PostPosted: Sat Mar 20, 2010 6:23 am 
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hardnstrong wrote:
friends
i understand that both options failed the zero test but why do we need a zero in set

ex- a set of 3 pen, 2 pencil and 0 flower
we can simply say it a set of 3 pen and 2 pencils, why do we consider something like zero in a set

Please explain

"zero" in this case does not imply an empty set; rather, it it a set consisting of an element-digit 0.

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  Re: M24 Q 33 [#permalink]
PostPosted: Sat Mar 20, 2010 8:48 am 
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