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If 20 percent of the students at a certain college take a writing

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Intern
Joined: 11 Oct 2017
Posts: 22
If 20 percent of the students at a certain college take a writing  [#permalink]

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16 Nov 2017, 17:56
1
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Difficulty:

55% (hard)

Question Stats:

57% (01:49) correct 43% (01:32) wrong based on 33 sessions

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If 20 percent of the students at a certain college take a writing class, what percent of the students at the college take a math class?

(1) 50 percent of the students who take a writing class also take a math class.

(2) 40 percent of the students who take a math class also take a writing class.

Math Expert
Joined: 02 Aug 2009
Posts: 7112
Re: If 20 percent of the students at a certain college take a writing  [#permalink]

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16 Nov 2017, 19:38
If 20 percent of the students at a certain college take a writing class, what percent of the students at the college take a math class?

(1) 50 percent of the students who take a writing class also take a math class.

(2) 40 percent of the students who take a math class also take a writing class.

Hi....

Individually each statement is clearly not sufficient..

So let's see them combined..
Let W be the number attending writing class and m be the number attending the math class.

Statement I and II both talk of the SAME set of people
So $$\frac{50w}{100}=\frac{40m}{100}.......w=0.8m$$...
But w is 20% of total.....
0.8m=0.2t......m=1/4t...
In% m=100t/4=25% of total
Sufficient

C
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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Joined: 21 Aug 2013
Posts: 1412
Location: India
Re: If 20 percent of the students at a certain college take a writing  [#permalink]

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17 Nov 2017, 10:42
As in the attached pic.

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IMG_20171118_000415.jpg [ 1.67 MiB | Viewed 477 times ]

Re: If 20 percent of the students at a certain college take a writing &nbs [#permalink] 17 Nov 2017, 10:42
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