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# In a graduate physics course, 70 percent of the students are male and

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Math Expert
Joined: 02 Sep 2009
Posts: 58427
In a graduate physics course, 70 percent of the students are male and  [#permalink]

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26 Nov 2014, 07:54
1
2
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Difficulty:

35% (medium)

Question Stats:

75% (01:48) correct 25% (02:28) wrong based on 190 sessions

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Tough and Tricky questions: Overlapping Sets.

In a graduate physics course, 70 percent of the students are male and 30 percent of the students are married. If two-sevenths of the male students are married, what fraction of the female students is single?

A. 2/7

B. 1/3

C. 1/2

D. 2/3

E. 5/7

Kudos for a correct solution.

Source: Chili Hot GMAT

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Re: In a graduate physics course, 70 percent of the students are male and  [#permalink]

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26 Nov 2014, 23:48
5

Using matrix method:
Attachment:

rat.png [ 4.31 KiB | Viewed 2990 times ]

1. Let total students = 100

2. Total male students = 70

3. Total married students = 30

4. Total female students = 100-70 = 30

5. Total unmarried students = 100-70 = 30

6. 2/7 th of male are married $$= \frac{2}{7} * 70 = 20$$

7. Married female students = 30-20 = 10

8. Female unmarried students = 30-10 = 20

Required fraction $$= \frac{20}{30} = \frac{2}{3}$$
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Re: In a graduate physics course, 70 percent of the students are male and  [#permalink]

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26 Nov 2014, 08:39
3
Let the universal set be X = {all students in the graduate physics course}, such that n(X) = 100
It will contain 2 mutually exclusive sets; M (all male students) & F (all female students), where n(M) = 70, n(F) = 30
Now 2/7 of all male students are married, implying their number = 20.

However the total number of married students = 30, implying 10 married females.

Therefore 20 single females; = 2/3 of total females.

Did i go wrong somewhere?
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Re: In a graduate physics course, 70 percent of the students are male and  [#permalink]

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26 Nov 2014, 09:21
1
Bunuel wrote:

Tough and Tricky questions: Overlapping Sets.

In a graduate physics course, 70 percent of the students are male and 30 percent of the students are married. If two-sevenths of the male students are married, what fraction of the female students is single?

A. 2/7

B. 1/3

C. 1/2

D. 2/3

E. 5/7

Kudos for a correct solution.

Source: Chili Hot GMAT

let assume there are 100 students of which 70 are male and 30 are females
if 30 are married then 70 will be single.
now its given that two-sevenths of the male students are married that means 2/7 of 70 = 20 males are married
if 30 is the total number of students who are married and out of that 20 are males then the remaining 10 will be females who are married.
total females = 30
married females = 10
then single females = 30-10 = 20
we need to find the fraction of female students who are single i.e single female students / total female student
= 20/30 = 2/3 [D]
it would be mare easy to visualize by using a tabular format....which i don't know how to draw in a post
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Re: In a graduate physics course, 70 percent of the students are male and  [#permalink]

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26 Nov 2014, 11:40
Let's assume a total of 100 students. From the premise we know that 70 are male and 30 are female. We also know that 30 are married and 70 are single. We're also told that (based on 100 students), 20 males are married--thus, 50 males are single. From this, we know that 10 females are married and 20 females are single.

20/30 females are single--2/3. Answer D
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Joined: 02 Sep 2009
Posts: 58427
Re: In a graduate physics course, 70 percent of the students are male and  [#permalink]

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27 Nov 2014, 07:42
Bunuel wrote:

Tough and Tricky questions: Overlapping Sets.

In a graduate physics course, 70 percent of the students are male and 30 percent of the students are married. If two-sevenths of the male students are married, what fraction of the female students is single?

A. 2/7

B. 1/3

C. 1/2

D. 2/3

E. 5/7

Kudos for a correct solution.

Source: Chili Hot GMAT

The correct answer is indeed D.
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Re: In a graduate physics course, 70 percent of the students are male and  [#permalink]

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09 Feb 2019, 07:37
Bunuel wrote:

Tough and Tricky questions: Overlapping Sets.

In a graduate physics course, 70 percent of the students are male and 30 percent of the students are married. If two-sevenths of the male students are married, what fraction of the female students is single?

A. 2/7

B. 1/3

C. 1/2

D. 2/3

E. 5/7

Kudos for a correct solution.

Source: Chili Hot GMAT

----------------Male--------Female
Married--------20------------10------------30
Single ---------50------------20------------70
----------------70-------------30-----------100

What fraction = 2/3

D
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Re: In a graduate physics course, 70 percent of the students are male and   [#permalink] 09 Feb 2019, 07:37
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