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# DS: Set

Author Message
SVP
Joined: 14 Dec 2004
Posts: 1689

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28 Jan 2006, 09:52
00:00

Difficulty:

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Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

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Please see the problem in the picture.
Attachments

Set Problem.JPG [ 41.3 KiB | Viewed 828 times ]

Manager
Joined: 15 Aug 2005
Posts: 198
Location: New York

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28 Jan 2006, 10:01
I got C

the numbers are

15, 3, 18 (total number of boys)
11, 10, 21(total number of girls)

26, 13
Director
Joined: 17 Dec 2005
Posts: 547
Location: Germany

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28 Jan 2006, 10:07
I have to use both facts.

1) You know 15 out of 18 boys study biology, so 3 do not

2) You can set up an equation, where x= number of girls not studying biology, z=girls studying biology and y number of boys not stuying it

z+x=2*(y+x)

1+2) x=5

So there are 34 students overall
SVP
Joined: 14 Dec 2004
Posts: 1689

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28 Jan 2006, 10:08
celiaXDN wrote:
I got C

the numbers are

15, 3, 18 (total number of boys)
11, 10, 21(total number of girls)

26, 13

celiaXDN,

The answer you got is correct but the numbers I think are wrong!
Manager
Joined: 15 Aug 2005
Posts: 198
Location: New York

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28 Jan 2006, 10:08
I have to use both facts.

1) You know 15 out of 18 boys study biology, so 3 do not

2) You can set up an equation, where x= number of girls not studying biology, z=girls studying biology and y number of boys not stuying it

z+x=2*(y+x)

1+2) x=5

So there are 34 students overall

I know what I got wrong now. I take 26 as the number of girls.
Manager
Joined: 15 Aug 2005
Posts: 198
Location: New York

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28 Jan 2006, 10:16
My new numbers

x= total number of girls

y= number of girls don't study biology

15, 3---------18
11, y----------x
26, x/2

so, 11+y = x
and 3+y = x/2

x= 16
total number of students 18+16=34.
VP
Joined: 21 Sep 2003
Posts: 1057
Location: USA

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28 Jan 2006, 10:19
I think it is B.

Total number of students = # Boys + # Girls = 18+2x

Total number of students = Total Biology + Total Non-Biology = 26+x

26+x = 18+2x

x = 8

or Total students = 34!

Is there anyuthing wrong?
_________________

"To dream anything that you want to dream, that is the beauty of the human mind. To do anything that you want to do, that is the strength of the human will. To trust yourself, to test your limits, that is the courage to succeed."

- Bernard Edmonds

SVP
Joined: 14 Dec 2004
Posts: 1689

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28 Jan 2006, 10:23
giddi77 wrote:
I think it is B.

Total number of students = # Boys + # Girls = 18+2x

Total number of students = Total Biology + Total Non-Biology = 26+x

26+x = 18+2x

x = 8

or Total students = 34!

Is there anyuthing wrong?

Wow Girish, at least I don't see anything wrong
Director
Joined: 17 Dec 2005
Posts: 547
Location: Germany

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28 Jan 2006, 10:24
giddi77 wrote:
I think it is B.

Total number of students = # Boys + # Girls = 18+2x

Total number of students = Total Biology + Total Non-Biology = 26+x

26+x = 18+2x

x = 8

or Total students = 34!

Is there anyuthing wrong?

no nothing wrong
SVP
Joined: 14 Dec 2004
Posts: 1689

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28 Jan 2006, 10:34
Well, this one is from GMAT sets, & the OA mentioned was "C"
but now we believe that it should be "B"
Very well done Girish!
VP
Joined: 21 Sep 2003
Posts: 1057
Location: USA

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28 Jan 2006, 10:34
vivek123 wrote:
giddi77 wrote:
I think it is B.

Total number of students = # Boys + # Girls = 18+2x

Total number of students = Total Biology + Total Non-Biology = 26+x

26+x = 18+2x

x = 8

or Total students = 34!

Is there anyuthing wrong?

Wow Girish, at least I don't see anything wrong

Once in a while I do get them right

I have been bitten by some of those tricky DS lately and I have improved a little bit.

So I have forced myself to read the #2 first, think carefully and then go to #1. This doesn't work in all cases. But try this on your next DS test and you will surely catch those tricky ones. Just my 0.02cents.
_________________

"To dream anything that you want to dream, that is the beauty of the human mind. To do anything that you want to do, that is the strength of the human will. To trust yourself, to test your limits, that is the courage to succeed."

- Bernard Edmonds

Manager
Joined: 15 Aug 2005
Posts: 198
Location: New York

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28 Jan 2006, 10:40
giddi77 wrote:
vivek123 wrote:
giddi77 wrote:
I think it is B.

Total number of students = # Boys + # Girls = 18+2x

Total number of students = Total Biology + Total Non-Biology = 26+x

26+x = 18+2x

x = 8

or Total students = 34!

Is there anyuthing wrong?

Wow Girish, at least I don't see anything wrong

Once in a while I do get them right

I have been bitten by some of those tricky DS lately and I have improved a little bit.

So I have forced myself to read the #2 first, think carefully and then go to #1. This doesn't work in all cases. But try this on your next DS test and you will surely catch those tricky ones. Just my 0.02cents.

DS is especially tricky. We need to be extra careful. Thanks for the advice. It is a useful approach.
Senior Manager
Joined: 11 Nov 2005
Posts: 328
Location: London

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28 Jan 2006, 16:44
I am not sure if this is right.

This approach assume that # of boys NOT studying Biology is 0. Shall we assume that????

if not then C remains the right answer!

vivek123 wrote:
giddi77 wrote:
I think it is B.

Total number of students = # Boys + # Girls = 18+2x

Total number of students = Total Biology + Total Non-Biology = 26+x

26+x = 18+2x

x = 8

or Total students = 34!

Is there anyuthing wrong?

Wow Girish, at least I don't see anything wrong
SVP
Joined: 16 Oct 2003
Posts: 1801

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28 Jan 2006, 18:37
I also got B.

26 + x = 18 + 2x
x = 8.
total students = 34
VP
Joined: 29 Dec 2005
Posts: 1341

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28 Jan 2006, 19:16
SunShine wrote:
I am not sure if this is right.
This approach assume that # of boys NOT studying Biology is 0. Shall we assume that????
if not then C remains the right answer!
vivek123 wrote:
giddi77 wrote:
I think it is B.
Total number of students = # Boys + # Girls = 18+2x
Total number of students = Total Biology + Total Non-Biology = 26+x
26+x = 18+2x
x = 8
or Total students = 34!
Is there anyuthing wrong?

Wow Girish, at least I don't see anything wrong

giddi77 is perfectly ok.

# of boys NOT studying Biology could be anything; it doesnot matter. The question is simply about the number of total students and B alone sufficiently provides that number.
So B is enough.
Manager
Joined: 31 Jan 2005
Posts: 143

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28 Jan 2006, 22:20
wow!!!!...great solution Girish......... good job

but was just curious to know....

how much time(minutes) u took to actually figure out that the answer is "B"
_________________

"Nothing is Impossible"

Senior Manager
Joined: 13 Jun 2005
Posts: 252
Location: Haverhill, MA

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29 Jan 2006, 10:59
My solution to this is B.

Kaplans math refrerence has a typical way of solving for such problems.

this is the 2005 book though.. i don't know about the new one.
29 Jan 2006, 10:59
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