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# M01-Q15

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VP
Joined: 03 Apr 2007
Posts: 1339

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16 Jul 2008, 20:25
1
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At Daifu university, 40% of all students are both members of a student organization and want to reduce their tuition costs. 20% of those students who want to reduce tuition are not members of the student organization. What percentage of all Daifu students want to reduce tuition?

(A) 20%
(B) 30%
(C) 40%
(D) 50%
(E) 60%

Source: GMAT Club Tests - hardest GMAT questions

REVISED VERSION OF THIS QUESTION IS HERE: m01-q15-67289.html#p1103452

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Director
Joined: 10 Sep 2007
Posts: 933

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16 Jul 2008, 20:31
3
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This is good example of grid question.
Attachments

Grid.doc [25 KiB]

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VP
Joined: 03 Apr 2007
Posts: 1339

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17 Jul 2008, 20:42
Thanks.
How do we need decide when to use sets and when to use grid?

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Director
Joined: 27 May 2008
Posts: 540

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17 Jul 2008, 21:24
8
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my 2 cents, practise venn diagram and always use it .... its more visual than grid and it makes me more confident about the right answer.

for this question

we need to find out (40+x)

and its given that (40+x) * 20/100 = x
x = 10

Attachment:

venn1.JPG [ 8.19 KiB | Viewed 11611 times ]

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Manager
Joined: 27 Jun 2008
Posts: 155

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18 Jul 2008, 23:56
True , for 2 sets I think Venn is the best way to go. For more than 2 grid makes things relatively simpler.

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Manager
Joined: 20 May 2008
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13 Sep 2008, 10:20
durgesh79 wrote:
my 2 cents, practise venn diagram and always use it .... its more visual than grid and it makes me more confident about the right answer.

for this question

we need to find out (40+x)

and its given that (40+x) * 20/100 = x
x = 10

Attachment:
venn1.JPG

durgesh for PRESIDENT....

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Director
Joined: 03 Jun 2009
Posts: 782

Kudos [?]: 925 [0], given: 56

Location: New Delhi
WE 1: 5.5 yrs in IT

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29 Jul 2009, 09:51
seems like question has changed a little.

Anyway, posting the latest question:
At Daifu university, 40% of all students are members of both a chess club and a swim team. If 20% of members of the swim team are not members of the chess club, what percentage of all Daifu students are members of the swim team?

The solution provided assumes that the students are either member of chess club or swim team or both. But no where in the question this has been mentioned.
I found it difficult to solve, since I didn't know how many students are member of neither of these clubs
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Intern
Joined: 31 Aug 2009
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01 Oct 2009, 20:46
irajeevsingh wrote:
True , for 2 sets I think Venn is the best way to go. For more than 2 grid makes things relatively simpler.

Is there a question on the GMATClub tests that uses 3 or more sets so I can practice the larger grid? So far I've always used Venn diagrams for solving these kinds of problems.

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Manager
Joined: 22 Aug 2009
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Location: UK

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28 Jan 2010, 14:39
Can anyone explain the answer for this ?

At Daifu university, 40% of all students are members of both a chess club and a swim team. If 20% of members of the swim team are not members of the chess club, what percentage of all Daifu students are members of the swim team?

20 %

30 %

40 %

50 %

60 %
_________________

FEB 15 2010 !!

well I would not disturb you after the D-day ..so please !!!

It Will Snow In Green , One Day !!!!

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Manager
Joined: 06 Oct 2009
Posts: 68

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05 Jul 2010, 05:33
Snowingreen wrote:
Can anyone explain the answer for this ?

At Daifu university, 40% of all students are members of both a chess club and a swim team. If 20% of members of the swim team are not members of the chess club, what percentage of all Daifu students are members of the swim team?

20 %

30 %

40 %

50 %

60 %

Hi Snowingreen,

The Answer here also is same D as this is a similar question as above.
Just replace "Members of student organization" with "members of chess club" and "students who want to reduce tuition fees" with "Members of swim club". Then refer Durgesh79's explanation above.
_________________

+1 kudos me if this is of any help...

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Manager
Joined: 28 Feb 2011
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07 Jul 2011, 08:57
IMO D.

We can easily rule out the first 3 options..I did not use the grid but it seems a viable option..
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Fight till you succeed like a gladiator..or doom your life which can be invincible

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Manager
Joined: 20 Dec 2010
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Schools: UNC Duke Kellogg

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08 Jul 2011, 09:52
The updated question is much clearer.

D it is..

% S (who only Swim) = (20/100) * ( .4 + S)

only S = 10.

Total S = 10 + 40 = 50

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Senior Manager
Joined: 19 Oct 2010
Posts: 251

Kudos [?]: 92 [1], given: 27

Location: India
GMAT 1: 560 Q36 V31
GPA: 3

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29 Jul 2011, 23:33
1
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oops.. I chose 60. Guess it's a common mistake.
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petrifiedbutstanding

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Senior Manager
Joined: 29 Jan 2011
Posts: 336

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24 Sep 2011, 17:18
bigoyal wrote:
seems like question has changed a little.

Anyway, posting the latest question:
At Daifu university, 40% of all students are members of both a chess club and a swim team. If 20% of members of the swim team are not members of the chess club, what percentage of all Daifu students are members of the swim team?

The solution provided assumes that the students are either member of chess club or swim team or both. But no where in the question this has been mentioned.
I found it difficult to solve, since I didn't know how many students are member of neither of these clubs

How to solve this using 2 x 2 grid?

Kudos [?]: 248 [0], given: 87

Intern
Joined: 04 Aug 2011
Posts: 41

Kudos [?]: 24 [0], given: 20

Location: United States
GMAT 1: 570 Q45 V25
GPA: 4
WE: Information Technology (Computer Software)

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14 Jan 2012, 21:12
if 20 % of swim club are not the member of chess then 80 % are member of chess.

Assume swim club has x members - then .8x = 40 solve for x you get x = 50 which makes the percentage of members overall in swim club as 50 %

IMO D

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Math Expert
Joined: 02 Sep 2009
Posts: 42606

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11 Jul 2012, 04:17
4
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Expert's post
1
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goalsnr wrote:
At Daifu university, 40% of all students are both members of a student organization and want to reduce their tuition costs. 20% of those students who want to reduce tuition are not members of the student organization. What percentage of all Daifu students want to reduce tuition?

(A) 20%
(B) 30%
(C) 40%
(D) 50%
(E) 60%

[Reveal] Spoiler: OA
D

Source: GMAT Club Tests - hardest GMAT questions

Can Someone please explain how to solve the above Question? I could'nt getmuch help from the OE.

Below is revised version of this question.

At Daifu university, 40% of all students are members of both a chess club and a swim team. If 20% of members of the swim team are not members of the chess club, what percentage of all Daifu students are members of the swim team?

A. 20%
B. 30%
C. 40%
D. 50%
E. 60%

Assume there are total of 100 students. 40 students are members of both clubs. We are told that: "20% of members of the swim team are not members of the chess club", thus if S is a # of members of the swim team then 0.2S is # of members of ONLY the swim teem:

40+0.2S=S --> S=50.

Or another way: since "20% of members of the swim team are not members of the chess club" then the rest 80% of members of the swim team (S) ARE members of the chess club, so members of both clubs: 0.8*S=40 --> S=50.

_________________

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Intern
Joined: 11 Jun 2012
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13 Jul 2012, 02:52
I will try creating a grid here

Student org No Student Org Total
Reduce Cost 40 x (40+x)

No Reduce Cost

Total 100

Now, says 20% of those who want to reduce cost are not part of student org
So, 20%( 40+x)=x => 80+2x =10x => x=10

so total number of students who want to reduce tuition is 40+x = 40+10=50

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Manager
Joined: 14 Jun 2012
Posts: 64

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22 Jul 2012, 08:33
Followed the grid method. Set up the grid correctly but used two variables instead of one. That led to taking more time. Good question with percentages on grid.

Concluded with D but since messed up the variables took abt a min more.
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Manager
Joined: 14 Dec 2012
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02 May 2013, 11:59
bunuel- u rock...
wat a simple expl.

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Intern
Joined: 21 Jun 2014
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26 Jun 2014, 05:30
You don't need grid to solve these kind of problems. Solve it using venn.

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Re: M01-Q15   [#permalink] 26 Jun 2014, 05:30

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# M01-Q15

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