Find all School-related info fast with the new School-Specific MBA Forum

It is currently 20 Oct 2014, 18:52

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

M20 Q35

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
1 KUDOS received
Senior Manager
Senior Manager
avatar
Joined: 20 Feb 2008
Posts: 296
Location: Bangalore, India
Schools: R1:Cornell, Yale, NYU. R2: Haas, MIT, Ross
Followers: 4

Kudos [?]: 28 [1] , given: 0

M20 Q35 [#permalink] New post 18 Nov 2008, 03:49
1
This post received
KUDOS
What is x ?

1. The median of set (x, 1, -1, 3, -x) is 0
2. The median of set (x, 1, -1, 3, -x) is \frac{x}{2}

Source: GMAT Club Tests - hardest GMAT questions
Kaplan Promo CodeKnewton GMAT Discount CodesVeritas Prep GMAT Discount Codes
1 KUDOS received
Director
Director
User avatar
Joined: 04 Jan 2008
Posts: 919
Followers: 52

Kudos [?]: 181 [1] , given: 17

Re: M20 Q35 [#permalink] New post 20 Nov 2008, 06:43
1
This post received
KUDOS
1 KUDOS received
CEO
CEO
User avatar
Joined: 29 Aug 2007
Posts: 2500
Followers: 54

Kudos [?]: 512 [1] , given: 19

Re: M20 Q35 [#permalink] New post 20 Nov 2008, 19:34
1
This post received
KUDOS
ventivish wrote:
What is x ?

1. The median of set (x, 1, -1, 3, -x) is 0
2. The median of set (x, 1, -1, 3, -x) is \frac{x}{2}


A.

1: x must be 0.
2: x could be 2 or 0.

If x = 2, then the set is [-2, -1, 1, 2, 3]. hence the median, x/2, is 1.
If x = 0, then the set is [-1, 0, 0, 1, 3]. hence the median, x/2, is 0.
_________________

Verbal: new-to-the-verbal-forum-please-read-this-first-77546.html
Math: new-to-the-math-forum-please-read-this-first-77764.html
Gmat: everything-you-need-to-prepare-for-the-gmat-revised-77983.html


GT

Senior Manager
Senior Manager
avatar
Joined: 20 Feb 2008
Posts: 296
Location: Bangalore, India
Schools: R1:Cornell, Yale, NYU. R2: Haas, MIT, Ross
Followers: 4

Kudos [?]: 28 [0], given: 0

Re: M20 Q35 [#permalink] New post 23 Nov 2008, 11:27
Hi thanks for answering this Q
The OA is A
And this is the OE
The median of a five-element set is necessarily a member of this set. No other member of the given set but x can be 0. S2 is not sufficient. x can be 2 or 0.

I could not get my head around to why the second statement was insufficient, I guess the median for an odd number of elements in a set must be a member ofthe set. And if x/2 is the median, then x/2 must be an integer, so x must either be 0 or 2. However the question stem does not state that x is an integer!

Thanks
Manager
Manager
avatar
Joined: 16 Apr 2008
Posts: 92
Followers: 1

Kudos [?]: 15 [0], given: 7

Re: M20 Q35 [#permalink] New post 29 Apr 2010, 06:08
I just picked some random numbers and hit S2 as invalid for x=2... But i will like a better approach.

Anyway, Answer is definitely option A (S1 suff.)

-Prabir
Intern
Intern
avatar
Joined: 29 Mar 2010
Posts: 16
Schools: UCLA, USC
WE 1: 3 Yr at leading SAAS company
Followers: 0

Kudos [?]: 4 [0], given: 0

Re: M20 Q35 [#permalink] New post 29 Apr 2010, 09:43
OA is A.

Median for set of odd numbers must be middle number in the sorted order.
Thus 0 means x or -x is middle number which implies x=0.

However St2 is never possible.

-Jvaidya
Manager
Manager
avatar
Joined: 18 Mar 2010
Posts: 90
Location: United States
GMAT 1: Q V
Followers: 2

Kudos [?]: 26 [0], given: 5

Re: M20 Q35 [#permalink] New post 29 Apr 2010, 10:17
jvaidya wrote:
OA is A.

Median for set of odd numbers must be middle number in the sorted order.
Thus 0 means x or -x is middle number which implies x=0.

However St2 is never possible.

-Jvaidya


Why wouldn't st2 be possible? With st2, x could be 0, making the median 0, or x could be 2, making the median 1.

I ordered the values in each way possible to find the answer. This was easy to do since there were an odd number of values, and since the values were the same for each statement.

-x, -1, 1, x, 3
-1, -x, x, 1, 3

The median would either have to be x or 1.
Intern
Intern
avatar
Joined: 29 Mar 2010
Posts: 16
Schools: UCLA, USC
WE 1: 3 Yr at leading SAAS company
Followers: 0

Kudos [?]: 4 [0], given: 0

Re: M20 Q35 [#permalink] New post 29 Apr 2010, 11:59
mmphf wrote:
jvaidya wrote:
OA is A.

Median for set of odd numbers must be middle number in the sorted order.
Thus 0 means x or -x is middle number which implies x=0.

However St2 is never possible.

-Jvaidya


Why wouldn't st2 be possible? With st2, x could be 0, making the median 0, or x could be 2, making the median 1.

I ordered the values in each way possible to find the answer. This was easy to do since there were an odd number of values, and since the values were the same for each statement.

-x, -1, 1, x, 3
-1, -x, x, 1, 3

The median would either have to be x or 1.


St2 alone will never be able to decide the value for x as it can be both 2 or 0 which is not true. However, St1 can give you 1 value i.e. x=0 which is correct.
Manager
Manager
avatar
Joined: 01 Dec 2008
Posts: 64
Followers: 0

Kudos [?]: 2 [0], given: 2

Re: M20 Q35 [#permalink] New post 30 Apr 2010, 04:49
I am a little bit confused here. The definition of a set is "A collection of distinct objects". Now if we choose A, then we are no longer dealing with a set.
And B does not help in identifying the answer either.
I feel that E is the answer, neither of these statements are sufficient to answer this question.
Manager
Manager
avatar
Joined: 18 Mar 2010
Posts: 90
Location: United States
GMAT 1: Q V
Followers: 2

Kudos [?]: 26 [0], given: 5

Re: M20 Q35 [#permalink] New post 30 Apr 2010, 12:38
aielman wrote:
I am a little bit confused here. The definition of a set is "A collection of distinct objects". Now if we choose A, then we are no longer dealing with a set.
And B does not help in identifying the answer either.
I feel that E is the answer, neither of these statements are sufficient to answer this question.


Why are we no longer dealing with a set if we pick "A" ? The value of x is the only thing that's in question. The numbers of the set do not change.
Manager
Manager
avatar
Joined: 01 Dec 2008
Posts: 64
Followers: 0

Kudos [?]: 2 [0], given: 2

Re: M20 Q35 [#permalink] New post 30 Apr 2010, 22:42
mmphf wrote:
aielman wrote:
I am a little bit confused here. The definition of a set is "A collection of distinct objects". Now if we choose A, then we are no longer dealing with a set.
And B does not help in identifying the answer either.
I feel that E is the answer, neither of these statements are sufficient to answer this question.


Why are we no longer dealing with a set if we pick "A" ? The value of x is the only thing that's in question. The numbers of the set do not change.


If the value of x is 0, then the set(lets call it A) now becomes
A={-1,-0,0,3}
There is no such thing as -0 and a +0
Therefore now the set A becomes
A={-1,0,0,3}
Now A can no longer be called a set, because the basic definition of a set is "A collection of distinct objects"
Senior Manager
Senior Manager
avatar
Joined: 24 Jul 2009
Posts: 298
Followers: 2

Kudos [?]: 72 [0], given: 0

Re: M20 Q35 [#permalink] New post 01 May 2010, 10:36
aielman wrote:
mmphf wrote:
aielman wrote:
I am a little bit confused here. The definition of a set is "A collection of distinct objects". Now if we choose A, then we are no longer dealing with a set.
And B does not help in identifying the answer either.
I feel that E is the answer, neither of these statements are sufficient to answer this question.


Why are we no longer dealing with a set if we pick "A" ? The value of x is the only thing that's in question. The numbers of the set do not change.


If the value of x is 0, then the set(lets call it A) now becomes
A={-1,-0,0,3}
There is no such thing as -0 and a +0
Therefore now the set A becomes
A={-1,0,0,3}
Now A can no longer be called a set, because the basic definition of a set is "A collection of distinct objects"



I would say, at least on GMAT-Land, until and unless it's explicitly mentioned that set contains distinct objects..DO not take it for granted. In many question, you fill find the concept of same elements in a given set..!!
Manager
Manager
avatar
Joined: 05 Mar 2010
Posts: 220
Followers: 1

Kudos [?]: 23 [0], given: 8

Re: M20 Q35 [#permalink] New post 02 May 2010, 01:54
Stmt 1 - x can only be zero

Stmt 2- here i need some explanation

Is 0/2 = 0 ????
If yes then 2/0 = ??
and 0/0 = ??

Can anyone please explain
_________________

Success is my Destiny

Senior Manager
Senior Manager
User avatar
Joined: 21 Dec 2009
Posts: 268
Location: India
Followers: 9

Kudos [?]: 72 [0], given: 25

Re: M20 Q35 [#permalink] New post 20 May 2010, 08:13
Stmt 1. The median of set (x, 1, -1, 3, -x) is 0

There are 5 no in the set and only x and -x are unknown. So x must be zero.



Stmt 2. The median of set (x, 1, -1, 3, -x) is \frac{x}{2}
x is variable here.

Answer is A
_________________

Cheers,
SD

SVP
SVP
avatar
Joined: 16 Nov 2010
Posts: 1691
Location: United States (IN)
Concentration: Strategy, Technology
Followers: 30

Kudos [?]: 297 [0], given: 36

Premium Member Reviews Badge
Re: M20 Q35 [#permalink] New post 03 May 2011, 04:29
(1)

-1,1,3 are remaning elements, so x = 0, for x to median (the 3rd element)

Sufficient.

(2)

-1,1,3 are remaning elements, but x can be 2, so that 1 = 2/2 is meian

or x = 6, so that 6/2 = 3 is a median.

Not Sufficient.

Answer - A
_________________

Formula of Life -> Achievement/Potential = k * Happiness (where k is a constant)

Get the best GMAT Prep Resources with GMAT Club Premium Membership

4 KUDOS received
Math Forum Moderator
avatar
Joined: 20 Dec 2010
Posts: 2045
Followers: 128

Kudos [?]: 952 [4] , given: 376

Re: M20 Q35 [#permalink] New post 03 May 2011, 11:20
4
This post received
KUDOS
timmyd wrote:
Not realy clear on the answer. Does anyone have another take on an explanation? Thanks!


My explanation is not going to be very different from others, but let me give it a shot. Please let me know if something is not clear.

Median of elements of any set arranged in ascending order will be the middle term if the number(count) of elements is odd.
Median of elements of any set arranged in ascending order will be the average of two middle terms if the number(count) of elements is even.

e.g.
A={-2,45,-56,0,23,-9,34}
Let's find the median of A:
Count= 7(Odd)
Arrange elements in ascending order:
A={-56,-9,-2,0,23,34,45}
Median is the middle term(because Count=7(odd)), i.e. {(Count+1)/2}th term.
Here, count=7; median will be (7+1)/2 i.e. 4th term.
4th term = 0 and is the median of the set.

One point worth noticing is that if the set has odd number of elements, Median must be one of its element. Like we saw, that "0" was one of the elements in the set.

case II:
B={-2,45,-56,0,23,-9,34,1}
Let's find the median of B:
Count= 8(Even)
Arrange elements in ascending order:
A={-56,-9,-2,0,1,23,34,45}
Median is the average of middle terms(because Count=8(Even)), i.e. Average of (Count/2)th term and ((Count/2)+1)th term.
Here, count=8; Count/2=4th term=0; And Count/2+1=4+1=5th term=1
Median = (0+1)/2 = 0.5
Thus, we saw that in case of even number of elements, median may be something other than any of the elements. Here 0.5 was not among the elements.

Coming to the question:

1.
Median of the set {x,1,-1,3,-x} is 0.
Count=5(Odd). Thus, we know that median must be one of the elements.
1 != 0
-1 != 0
3 != 0
Only, x or -x can be 0
x=0
Or
-x=0 i.e. x=0
We know for sure that x=0
Sufficient.

2.
Median of {x,1,-1,3,-x} is x/2.
Count=5(Odd)

Means; x/2 must be one among 1,-1,3,x or -x for we know that median of odd number of elements must be one of the elements itself.

Let's check one by one;
Say; Median = x
Means; x/2=x; It is possible only for x=0. If x=0
{x,1,-1,3,-x} becomes {-1,0,0,1,3}. Median=0, which is true.
So; x could be "0". But, we must try the same thing for other numbers as well.

Say; Median=1
i.e. x/2=1; x=2;
{x,1,-1,3,-x} becomes {-2,-1,1,3,2}. Median=1, which is true.
What we saw here that; x could be 2 as well.
If we made x=2; the median becomes 1, which is x/2; supporting the statement.

We already have two possible values of x; 0 and 2. We can stop here.
Not Sufficient.

Ans: "A"

Note: We could have also checked for other numbers:
Say; Median = 3
x/2=3
x=6
{x,1,-1,3,-x} becomes {-6,-1,1,3,6}. Median=1, which is false.
x/2=6/2=3; According to the statement, Median should be 3, but we got our median as 1. Thus, x can't be 6.

Say; Median = -1
x/2=-1
x=-2
{x,1,-1,3,-x} becomes {-2,-1,1,2,3}. Median=1, which is false.
x/2=-2/2=-1; According to the statement, Median should be -1, but we got our median as 1. Thus, x can't be -2.

Say; Median = -x
-x/2=-x, which is x/2=x. Same as first
x can be 0.
_________________

~fluke

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Manager
Manager
avatar
Joined: 17 Mar 2010
Posts: 65
Location: Hyderabad, India
WE 1: Deloitte 3 yrs
WE 2: Prok going on
Followers: 1

Kudos [?]: 13 [0], given: 2

Re: M20 Q35 [#permalink] New post 03 May 2011, 21:49
ventivish wrote:
What is x ?

1. The median of set (x, 1, -1, 3, -x) is 0
2. The median of set (x, 1, -1, 3, -x) is \frac{x}{2}

[Reveal] Spoiler: OA
A

Source: GMAT Club Tests - hardest GMAT questions


We have five numbers: -1,-x,x,1,3 and median has to be the middle number that is the 3rd number in the list.

Statement One:

These five numbers can be arranged in the following fashion:

1) -x, -1, 1, x, 3 (x can be 2 say)
2) -x, -1, 1, 3, x (x can be 4 say)
3) -1, -x, x, 1, 3 (x is 0<= x <= 1)

Now for these three possibilities median will be 1, 1 and x but we know it is zero so it implies x = 0.

So Statement One alone is enough.

Statement two:

We have same set of numbers and same set of possibilities. So if median is \frac{x}{2} it means

1) x is 2 and numbers are: -2, -1, 1, 2, 3. x can not be 1 right????
2) x cannot be 2 as 3 is not less than 2 so leave this here.
3) x can only be zero and 0 divided be zero is again zero.

So x can be 0 and 2. Statement 2 alone is not enough.

So Answer is A.
_________________

Akhil Mittal

I have not failed. I've just found 10000 ways that won't work. Thomas A. Edison

If my post was helpful to you then encourage me by your kudos :)

Intern
Intern
avatar
Joined: 06 Apr 2012
Posts: 10
Followers: 0

Kudos [?]: 1 [0], given: 34

Re: M20 Q35 [#permalink] New post 07 May 2012, 06:14
from 1. x has to be zero to satisfy the given condition
from 2. x may be 0 or 2.
hence 1 alone is sufficient to answer the question.
my take option A
Intern
Intern
avatar
Joined: 11 Jan 2010
Posts: 38
Followers: 1

Kudos [?]: 50 [0], given: 6

Re: M20 Q35 [#permalink] New post 08 May 2013, 05:10
Question: x = ?

S1: Set = {x, -1, 1, 3, -x} and Median = 0
There are five terms and the median will be zero only if x = 0
S1 is sufficient. Eliminate BCE.

S2: Set = {x, -1, 1, 3, -x} and Median = x/2
If x = 2 => Set = {-2, -1, 1, 2, 3} => Median = 1
If x = 0 => Set = {-1, 0, 0, 1, 3} => Median = 0
So, S2 is true for at least two values of x.
S2 is not sufficient. Eliminate D.

Correct answer is A.
Expert Post
2 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 23348
Followers: 3602

Kudos [?]: 28659 [2] , given: 2808

Re: M20 Q35 [#permalink] New post 08 May 2013, 05:38
2
This post received
KUDOS
Expert's post
1
This post was
BOOKMARKED
What is the value of x?

Note that the median of a set with odd number of elements is just the middle element, when arranged in ascending/descending order.

(1) The median of set \{x, -1, 1, 3, -x\} is 0. The median of this set of 5 (odd) elements must be the middle term, hence x=0. Sufficient.

(2) The median of set \{x, -1, 1, 3, -x\} is \frac{x}{2}. It could be that x=0 (in this case the set is {-1, 0, 0, 1, 3}) as well as it could be that x=2 (in this case the set is {-2, -1, 1, 2, 3}). Not sufficient.

Answer: A.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Re: M20 Q35   [#permalink] 08 May 2013, 05:38
    Similar topics Author Replies Last post
Similar
Topics:
q 35 discussion woodahy 1 29 Aug 2010, 06:12
M12 Q35 ichha148 2 21 Apr 2010, 16:39
M12 Q35 gmatjon 3 03 Jan 2010, 18:40
m01 q35 prathns 1 27 Dec 2009, 01:49
25 Experts publish their posts in the topic M10 Q35 gk2k2 29 21 Dec 2008, 10:13
Display posts from previous: Sort by

M20 Q35

  Question banks Downloads My Bookmarks Reviews Important topics  

Go to page    1   2    Next  [ 22 posts ] 

Moderators: Bunuel, WoundedTiger



GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.