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Difficult DS problem in the spirit of elections

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Difficult DS problem in the spirit of elections

by madsport » Tue Aug 26, 2008 12:00 pm
All the members of club Y are either Democrats or Repulicans. If 1/2 of the male members and 3/5 of the female members are Democrats, what is the ratio of the number of males to the number of females in the club?

(1) In club Y the number of females members is one less than the number of male members.

(2) In club Y the number of male Republican members is equal to the number of female Democratic members.
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by saeed » Tue Aug 26, 2008 12:20 pm
I think the answer is B. Because from statement 2 we can get the ratio of m/f.
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by madsport » Tue Aug 26, 2008 12:23 pm
Yes, the correction answer is B. Can you explain this further?
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Re: Difficult DS problem in the spirit of elections

by Stuart@KaplanGMAT » Tue Aug 26, 2008 12:27 pm
madsport wrote:All the members of club Y are either Democrats or Repulicans. If 1/2 of the male members and 3/5 of the female members are Democrats, what is the ratio of the number of males to the number of females in the club?

(1) In club Y the number of females members is one less than the number of male members.

(2) In club Y the number of male Republican members is equal to the number of female Democratic members.
We want to solve for m/f.

(1) f = m - 1

No way to get m/f out of this: insufficient.

(2) Male(rep) = Female(Dem)

Well, if 1/2 of the males are democrats, then half are republicans. So, (2) tells us that:

(1/2)m = (3/5)f

We can certainly rearrange this to solve for m/f: sufficient.

(2) is sufficient, (1) isn't: choose (B).

As an aside, here's the math for (2):

(1/2)m = (3/5)f
(1/2)m / f = (3/5)
m/f = (3/5)/(1/2)
m/f = (3/5)*(2/1)
m/f = 6/5

Of course, we never actually want to do the math if we can avoid it - as soon as you can see that our equation can be manipulated to

m/f=some number

you know you have enough information to solve.
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