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A business school event invites all of its graduate and unde [#permalink]

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27 May 2014, 18:01

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A business school event invites all of its graduate and undergraduate students to attend. Of the students who attend, male graduate students outnumber male undergraduates by a ratio of 7 to 2, and females constitute 70% of the group. If undergraduate students make up 1/6 of the group, which of the following CANNOT represent the number of female graduate students at the event?

A) 18 B) 27 C) 36 D) 72 E) 180

I tried to solve using a Double Set Matrix:

------------------Male--------Female---------Total Graduate 7x 2x 9x Under Graduate - - (1/6)100 Total 30 70 100

Is it correct here to take the Total as 100 since it is mentioned that females constitute 70% of the group or should the total be an unknown x? Thanks for your help.

A business school event invites all of its graduate and undergraduate students to attend. Of the students who attend, male graduate students outnumber male undergraduates by a ratio of 7 to 2, and females constitute 70% of the group. If undergraduate students make up 1/6 of the group, which of the following CANNOT represent the number of female graduate students at the event?

------------------Male--------Female---------Total Graduate 7x 2x 9x Under Graduate - - (1/6)100 Total 30 70 100

Is it correct here to take the Total as 100 since it is mentioned that females constitute 70% of the group or should the total be an unknown x? Thanks for your help.

Female students make up 70% of the group and so male students make up 30% of the group. 9x = (30/100)*Total Total = 30x (we got the total number of students in terms of x)

A business school event invites all of its graduate and undergraduate students to attend. Of the students who attend, male graduate students outnumber male undergraduates by a ratio of 7 to 2, and females constitute 70% of the group. If undergraduate students make up 1/6 of the group, which of the following CANNOT represent the number of female graduate students at the event?

------------------Male--------Female---------Total Graduate 7x 2x 9x Under Graduate - - (1/6)100 Total 30 70 100

Is it correct here to take the Total as 100 since it is mentioned that females constitute 70% of the group or should the total be an unknown x? Thanks for your help.

Regards, Sri

If you do assume the total to be 100, you will get fractions at places since the total is 30x. So the total must be a multiple of 30. In such cases, it is best to get everything in a single variable.
_________________

A business school event invites all of its graduate and undergraduate students to attend. Of the students who attend, male graduate students outnumber male undergraduates by a ratio of 7 to 2, and females constitute 70% of the group. If undergraduate students make up 1/6 of the group, which of the following CANNOT represent the number of female graduate students at the event?

------------------Male--------Female---------Total Graduate 7x 2x 9x Under Graduate - - (1/6)100 Total 30 70 100

Is it correct here to take the Total as 100 since it is mentioned that females constitute 70% of the group or should the total be an unknown x? Thanks for your help.

Female students make up 70% of the group and so male students make up 30% of the group. 9x = (30/100)*Total Total = 30x (we got the total number of students in terms of x)

Re: A business school event invites all of its graduate and unde [#permalink]

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09 Jun 2014, 08:10

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A business school event invites all of its graduate and undergraduate students to attend. Of the students who attend, male graduate students outnumber male undergraduates by a ratio of 7 to 2, and females constitute 70% of the group. If undergraduate students make up 1/6 of the group, which of the following CANNOT represent the number of female graduate students at the event?

I solved this question in a different way and stuck:

I considered total students = X

Females 70% of X Males 30% of X

Male grad to undergrad ratio = 7:2

Therefore male undergrads in X = 2/9 * 3/10 X

= 1/15 * X

1/6 of the group are undergrad, i.e 1/6 * X

Female undergrad = 1/6 * X - 1/15 * X = X/10

Thus, Female grad = (7/10 * X )- X/10 = 3/5 * X

As per my solution Female grad number must be divisible by 3 and all choices are divisible by 3. I am not able to identify any error in my approach.. please help to identify mistake in my solution.
_________________

Piyush K ----------------------- Our greatest weakness lies in giving up. The most certain way to succeed is to try just one more time. ― Thomas A. Edison Don't forget to press--> Kudos My Articles: 1. WOULD: when to use?| 2. All GMATPrep RCs (New) Tip: Before exam a week earlier don't forget to exhaust all gmatprep problems specially for "sentence correction".

A business school event invites all of its graduate and undergraduate students to attend. Of the students who attend, male graduate students outnumber male undergraduates by a ratio of 7 to 2, and females constitute 70% of the group. If undergraduate students make up 1/6 of the group, which of the following CANNOT represent the number of female graduate students at the event?

I solved this question in a different way and stuck:

I considered total students = X

Females 70% of X Males 30% of X

Male grad to undergrad ratio = 7:2

Therefore male undergrads in X = 2/9 * 3/10 X

= 1/15 * X

1/6 of the group are undergrad, i.e 1/6 * X

Female undergrad = 1/6 * X - 1/15 * X = X/10

Thus, Female grad = (7/10 * X )- X/10 = 3/5 * X

As per my solution Female grad number must be divisible by 3 and all choices are divisible by 3. I am not able to identify any error in my approach.. please help to identify mistake in my solution.

You get that Number of female grads is (3/5)*X. Note that X needs to be divisible by 10 since number of female is 7/10*X, number of males is 3/10*X etc. So X should be a multiple of 2. Since number of female grads is (3/5)*X, number of female grads should be a multiple of 2 too. So 27 is not possible.
_________________

If we take LCM of the denominators i.e. 9,10 and 6, we get 90.

Wouldnt this mean that this group HAS TO HAVE the total number of students in multiples of 90. If so then FG would be 54/90 or 3/5 or 60% of the group to be Female Grads. Only 27 is the number which is not a multiple of 6, hence thats the correct answer.

Re: A business school event invites all of its graduate and unde [#permalink]

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26 Jul 2015, 09:09

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: A business school event invites all of its graduate and unde [#permalink]

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01 Apr 2016, 21:52

VeritasPrepKarishma wrote:

gmattesttaker2 wrote:

Hello,

Can you please assist with this:

A business school event invites all of its graduate and undergraduate students to attend. Of the students who attend, male graduate students outnumber male undergraduates by a ratio of 7 to 2, and females constitute 70% of the group. If undergraduate students make up 1/6 of the group, which of the following CANNOT represent the number of female graduate students at the event?

------------------Male--------Female---------Total Graduate 7x 2x 9x Under Graduate - - (1/6)100 Total 30 70 100

Is it correct here to take the Total as 100 since it is mentioned that females constitute 70% of the group or should the total be an unknown x? Thanks for your help.

Female students make up 70% of the group and so male students make up 30% of the group. 9x = (30/100)*Total Total = 30x (we got the total number of students in terms of x)

So undergrad females must be 3x and grad females must be 18x.

Number of Grad females must be a multiple of 18. 27 is not a multiple of 18 so it cannot be the number of grad females. Answer (B)

I really like your posts Karishma, superb explanations. My only concern there are times I don't know how to approach a question, but after reading your explanations it makes perfect sense. How do i work on this?

Re: A business school event invites all of its graduate and unde [#permalink]

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16 Sep 2017, 10:00

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
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