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DS: Set

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DS: Set [#permalink] New post 28 Jan 2006, 08:52
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
Please see the problem in the picture.
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 [#permalink] New post 28 Jan 2006, 09:01
I got C

the numbers are

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

26, 13
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 [#permalink] New post 28 Jan 2006, 09:07
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
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 [#permalink] New post 28 Jan 2006, 09:08
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!
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 [#permalink] New post 28 Jan 2006, 09:08
allabout wrote:
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. :(
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 [#permalink] New post 28 Jan 2006, 09:16
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.
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 [#permalink] New post 28 Jan 2006, 09:19
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?
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 [#permalink] New post 28 Jan 2006, 09:23
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 :-D
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 [#permalink] New post 28 Jan 2006, 09:24
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?
:wink:

no nothing wrong
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 [#permalink] New post 28 Jan 2006, 09:34
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!
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 [#permalink] New post 28 Jan 2006, 09:34
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 :-D


Once in a while I do get them right :lol:

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.
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 [#permalink] New post 28 Jan 2006, 09:40
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 :-D


Once in a while I do get them right :lol:

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.
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 [#permalink] New post 28 Jan 2006, 15:44
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 :-D
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 [#permalink] New post 28 Jan 2006, 17:37
I also got B.

26 + x = 18 + 2x
x = 8.
total students = 34
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 [#permalink] New post 28 Jan 2006, 18:16
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 :-D


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.
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 [#permalink] New post 28 Jan 2006, 21:20
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"
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 [#permalink] New post 29 Jan 2006, 09:59
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.
  [#permalink] 29 Jan 2006, 09:59
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