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percentage

by oldheaven » Tue Dec 20, 2011 5:57 am
30% of the students of a university are studying Engineering.60 percent of students are male and the number of female students studying medicine is 15% of all of the students.what percentage of the students studying Engineering is male?

1)12%
2)16.7%
3)9%
4)5%
5)8%
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by pemdas » Wed Dec 21, 2011 11:59 am
the number of female students studying medicine is 15% of all of the students -> .15S=x*0.4S and x=150/4=37.5 % of female students are studying medicine, the rest are assumed a) either to study engineering or b) to study Engineering and not to study anything
case a) 37.5% of females study engineering, which is 37.5 * 40% of total students, leaves 15% of all students who study Engineering
case b) less than 37.5% of females study engineering, which is less than 15% of all students who study Engineering.

Considering 60% of all students are male, only male >15% can study Engineering.

ans b, 16.7%
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by deepans » Wed Dec 21, 2011 12:34 pm
I think the answer is D) 5%

I assumed students studying Engineering and Math are mutually exclusive. So,

Assume total students = 100
Male - 60 (given)
So Female - 40
Female Math students - 15 (given)
Female Engg students - 25 (40-15)
Total Engg - 30 (given)
So Male Engg - 5 (30-25)
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by LalaB » Wed Dec 21, 2011 12:43 pm
lets assume,that we have 100 students in total.

then 15% of all of the students = .15*100=15 female students studying medicine

since in total we have 40 females (0.4*100), then 40-15=25 females study engineering

since we have 30 (0.3*100) students studying engineering 30-25=5 males studying engineering

5/100=5%
Last edited by LalaB on Thu Dec 22, 2011 7:54 am, edited 1 time in total.
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by pemdas » Thu Dec 22, 2011 1:08 am
the ratio 1/6 returns 16.7%
accordingly 1/6=10/60 would return 9, 18 and 24 students for 15%,30% and 40% of 60 students. Or take # students as 120, 180 etc.

we don't know how many female students study engineering; we only know that 15 female students study medicine and can effectively infer:
- 15 female students studying medicine may study engineering too (no room for assuming mutual exclusiveness here, as no restriction is put in q.)
- 15 female students studying medicine may not study engineering
Last edited by pemdas on Thu Dec 22, 2011 2:50 am, edited 1 time in total.
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by smackmartine » Thu Dec 22, 2011 1:27 am
IMO B, use 2X2 matrix method: easy: reliable: faster
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by pemdas » Thu Dec 22, 2011 2:11 am
nice, worth to stress
oldheaven wrote:30% of the students of a university are studying Engineering.60 percent of students are male and the number of female students studying medicine is 15% of all of the students.what percentage of the students studying Engineering is male?
obviously not 5/100 but 5/30 with the same proportion set as 1/6
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by user123321 » Thu Dec 22, 2011 5:37 am
Nice question. I agree with pemdas. It should be 5/30. as we need to find it as a percentage of total engineering canditates.

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by Bharath Krishnan » Thu Dec 22, 2011 7:10 am
Question is "what percentage of the students studying Engineering is male?"

We have found out the the number of male engineering students is 5 out of a pool of 100 students.

The answer should be B) 16.7% - which is x percent of 30 engineering students equals 5 male engineering students [(x/100)*30=5 or (5/30)*100=x]

The answer choice D) 5% is incorrect because it is the percentage of male students from a pool of 100 students (includes Engineering and Medicine) while the question asks from a pool of 30 engineering questions.

Note: I have considered the total pool of students to be 100 since we are dealing with percentages.

Thanks,
Bharath-[/b]
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by LalaB » Thu Dec 22, 2011 7:54 am
yep, I got where I was wrong. thnx a lot, guys!
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by oldheaven » Thu Dec 22, 2011 8:22 am
pemdas wrote:the number of female students studying medicine is 15% of all of the students -> .15S=x*0.4S and x=150/4=37.5 % of female students are studying medicine, the rest are assumed a) either to study engineering or b) to study Engineering and not to study anything
case a) 37.5% of females study engineering, which is 37.5 * 40% of total students, leaves 15% of all students who study Engineering
case b) less than 37.5% of females study engineering, which is less than 15% of all students who study Engineering.

Considering 60% of all students are male, only male >15% can study Engineering.

ans b, 16.7%
I really enjoy your approach and style, thank you pemdas.
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