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DS - males/females college

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DS - males/females college

by ccassel » Tue Apr 26, 2011 3:07 pm
What fraction of this year graduation students at a certain college are males ?
1. Of this year graduating students, 33% of the males and 20% of the females transferred from another college.
2. Of this year's graduating students, 25% transferred from another college.


The answer is C but what do we know about the students that did NOT transfer from another college that graduated from this college?

With the information requested by the question, should'nt the equation be?...
graduating male transfered students + graduating male NON-transfer students = total graduating male students

cheers,
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by Tani » Tue Apr 26, 2011 3:49 pm
Try this when putting the two statement together (M = # males, F= # females)

.33M + .20F = .25(M+F)
.33M + .20 F = .25M + .25 F
.08M = .05F
ratio of males to females = .05/.08 = 5/8

You still don't know how many, but you can tell the ratio
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by Testluv » Tue Apr 26, 2011 6:35 pm
ccassel wrote:
The answer is C but what do we know about the students that did NOT transfer from another college that graduated from this college?

With the information requested by the question, should'nt the equation be?...
graduating male transfered students + graduating male NON-transfer students = total graduating male students

cheers,
That equation is correct. However, we also know that:

transfer males + transfer females = total transferred

That`s the equation the above expert used.

Some pattern recognition can also help here. Since both transfer males and transfer females will contribute to the total transfer students according to their proper weights, we can view this as a weighted average problem where:

20-------25------------33
(f)-----overall--------(m)

Since females are closer to the overall average, there must be more females than males. In particular, females are 5 away from overall while males are 8 away. Thus, the ratio of males to females is just 5 to 8 (the inverse of the ratio of each group`s distance from overall).
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