If 2/5 of the students at College C (GMATPrep)

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If 2/5 of the students at College C are business majors, what is the number of female students at College C?

1) 2/5 of the male students at College C are business majors.
2) 200 of the female students at College C are business majors.

OA: C



Would anyone please explain?

I answer B because I thought that:

From the info:
2/5 * (total) = business major
total = M + F
2/5 * (M + F) = business major
2/5*M + 2/5*F = business major

1) 2/5*M are business major (I thought we already know that from the information given)

2) 2/5*F = 200 so F = 500

That's why I thought statement 2 alone is sufficient....would anyone please explain at which point I was wrong???

Appreciate all the help!

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by tohellandback » Mon Aug 10, 2009 9:45 pm
you are right!!
just one mistake..
you combined the information you got from the statement 1 with the information from 2.
and thats why the answer should be C.

2/5*M are business major-- thats not from the question stem. thats from statement 1.
The powers of two are bloody impolite!!

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by georgeung » Tue Aug 11, 2009 1:59 pm
Can you not simplify the problem as Freshy had done?

I understand what he had done by believing he already had data 1, but I want to say that kind of simplification cannot be done and I'm hoping someone can explain it to me.

That was pretty slick how you did that, Freshy. I didn't think about doing that.

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by tohellandback » Tue Aug 11, 2009 5:47 pm
georgeung wrote:Can you not simplify the problem as Freshy had done?

I understand what he had done by believing he already had data 1, but I want to say that kind of simplification cannot be done and I'm hoping someone can explain it to me.

That was pretty slick how you did that, Freshy. I didn't think about doing that.
you can of course do it.
lets say there are 100 students...
40 male and 60 female. if we say 2/5 of the students are business majors.
and if you know that 2/5 of male are business majors. then 2/5 of the remaining group..i.e. females must be business majors.
The powers of two are bloody impolite!!

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by ben wade » Tue Aug 11, 2009 11:05 pm
the mistake freshy makes is that
because (2/5)T = BM
and T = M+F

we can not assume (2/5)M + (2/5)F = BM
It should be (2/5)(M+F) = (x)M + (y)F.

From st 1: (x)M = (2/5)M

which gives us (2/5)(M+F) = (2/5)M + (y)F
but it is insufficient as it does not give a value for F
However, we get to know that (y)F has to be (2/5)F

St2: says (y)F = 200
but we do not know y. (y can 2/5 or 3/5....)
so Insuff

combining the 2,
we get to know that (y)F = (2/5)F = 200.
So F = 500.
Hence C.

Hope this helps.

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by georgeung » Wed Aug 12, 2009 6:44 am
That did help. THank you for answering that.

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by adilka » Thu Aug 13, 2009 9:55 am
ben wade wrote:the mistake freshy makes is that
because (2/5)T = BM
and T = M+F

we can not assume (2/5)M + (2/5)F = BM
It should be (2/5)(M+F) = (x)M + (y)F.
That's where I'm not totally clear. I operate based on mathematical principles, so based on a simple principle that
x*(a+b)=x*a+x*b

What is wrong with assuming that

2/5*(M+F) not equal to 2/5*M+ 2/5*F

i know im making some sort of an implicit assumption wrong but can't put a finger to it.