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Re: data suffeciency [#permalink]
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First of all, we need to be able to find a solid number,the total number of guest, as an answer.

The only solid number we are given to work with is 15, the number of hamburgers eaten by the guests.

From the question we could see that the guests can be broken down into 4 categories.

VEGETARIAN STUDENT (V & S)
NON-VEGETARIAN STUDENT (NV & S)
VEGETARIAN NON-STUDENT (V & NS)
NON-VEGETARIAN NON-STUDENT (NV & NS)

Looking @ # of hamburgers eaten,

The question states that (NV & NS) ate exactly 1 hamburger and that
no hamburger was eaten by any guest who was a student, hamburger eaten by (V & S) = (NV & S) = 0; a vegetarian, hamburger eaten by (V & S) = (V & NS) =0; or both, hamburger eaten by (V & S) = 0.

So from this we can conclude the # of (NV & NS) = 15.

The last piece of information given is that 1/2 Total = V, which also means 1/2 Total = NV, where NV + V = Total and NS + S = Total. Drawing a table can help understand this relationship.



Statement 1:

The vegetarians attended the party at a rate of 2 students to every 3 non-students, half the rate for non-vegetarians.

I think this should be reworded to ratio instead of rate.

Anyways this just means that for every 2 (V & S) there are 3 (V & NS), which is half the ratio of S to NS for NV. Therefore for every 4 (NV & S) there are 3 (NV & NS), which means \(\frac{4}{3}=\frac{(NV & S)}{(NV & NS)}\)

Since we know that (NV & NS) = 15. We can solve for (NV & S) and Find Total because 1/2* Total = (NV & NS) + (NV & S)

Sufficient.

Statement 2:

30% of the guests were vegetarian non-students.

This give us no way to link 15 to the total number of guest. So insufficient.

This is more clear if you draw a table to help visualize things.

I'm sure someone will come up with a better explanation later, but I hope this can help till then.

Originally posted by chaoswithin on 09 Nov 2010, 12:15.
Last edited by chaoswithin on 09 Nov 2010, 12:24, edited 2 times in total.
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Re: data suffeciency [#permalink]
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mrinal2100 wrote:
Guests at a recent party ate a total of fifteen hamburgers. Each guest who was neither a student nor a vegetarian ate exactly one hamburger. No hamburger was eaten by any guest who was a student, a vegetarian, or both. If half of the guests were vegetarians, how many guests attended the party?

(1) The vegetarians attended the party at a rate of 2 students to every 3 non-students, half the rate for non-vegetarians.

(2) 30% of the guests were vegetarian non-students.


can someone explain in detail


This is what I drew when I read the Question stem. Half of the guests were vegetarians so Total/2 stands for the complete vegetarian circle. All outside Vegetarian circle are Total/2.
Attachment:
Ques.jpg
Ques.jpg [ 17.29 KiB | Viewed 49381 times ]


Statement 1: Veg students : Veg non students = 2:3
Let me say they are 2x and 3x in number.

Non veg students : Non veg non-students = 4:3 (Since veg's ratio is half of non veg's ratio)
Let me say they are 4y and 3y in number.
So now my diagram looks like this:
Attachment:
Ques1.jpg
Ques1.jpg [ 18.33 KiB | Viewed 49317 times ]


3y = 15 hence y = 5
Since 7y is half of the total, 35 is half of the total. So total number of students is 70. Sufficient.

Statement 2: We get that 30% of the guests were veg non students and we already know that 50% of the guests are veg so 20% of the guests are veg students. Essentially, we have got the 3:2 ratio of above. But we do not have the 4:3 ratio of above hence we cannot equate 15 to anything. Therefore, statement 2 is not sufficient alone.
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Re: Guests at a recent party ate a total of fifteen hamburgers. [#permalink]
Good one!
Stumbled in the test. I like the MGMAT solution.

Non veg - Non Students is 15.

Since Nonveg Student to non student ratio is 4:3, therefore non veg students will be 20.
4/3=x/15
Therefore x= 20. That makes 35 NV and 35 Veg so total 70
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Re: Guests at a recent party ate a totaal of [#permalink]
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nitzz wrote:
Guests at a recent party ate a total of fifteen hamburgers. Each guest who was neither a student nor a vegetarian ate exactly one hamburger. No hamburger was eaten by any guest who was a student, a vegetarian, or both. If half of the guests were vegetarians, how many guests attended the party?

(1) The vegetarians attended the party at a rate of 2 students to every 3 non-students, half the rate for non-vegetarians.

(2) 30% of the guests were vegetarian non-students.


St 1: Sufficient: Veg attended in 2:3 so the Non veg attended in ratio 4:3. We now from Question stem Non veg - Non student ate 15 burgers. therefore Non veg attended the party in 20:15 (4:3). Total no of Non Veg = 35 nos. And total guests = 2*35=70 (from Question Stem).
St 2: Not sufficient: cant calculate other group of non-veg and only %age is provided.

Hence Answer A.

Originally posted by SOURH7WK on 20 Oct 2012, 23:59.
Last edited by SOURH7WK on 21 Oct 2012, 09:36, edited 1 time in total.
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Guests at a recent party ate a total of fifteen hamburgers. [#permalink]
Bunuel, could you explain this statement: " --> so, non-vegetarian non-students compose 3/7 of all non vegetarians." Don't see how you get there. Thanks!

Originally posted by Krage17 on 01 Dec 2014, 05:54.
Last edited by Krage17 on 01 Dec 2014, 07:34, edited 1 time in total.
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Guests at a recent party ate a total of fifteen hamburgers. [#permalink]
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Krage17 wrote:
Bunuel, could you explain this statement: " --> so, non-vegetarian non-students compose 3/7 of all non vegetarians." Don't see how you there. Thanks!


Since non-vegetarian students plus non-vegetarian non-students equals all non-vegetarians, then (non-vegetarian non-students/(total) = 3/(4 + 3) = 3/7.

Hope it's clear.
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Re: Guests at a recent party ate a total of fifteen hamburgers. [#permalink]
It is. Took me a while to grasp it.

Bunuel wrote:
Krage17 wrote:
Bunuel, could you explain this statement: " --> so, non-vegetarian non-students compose 3/7 of all non vegetarians." Don't see how you there. Thanks!


Since non-vegetarian students plus non-vegetarian non-students equals all non-vegetarians, then (non-vegetarian non-students/(total) = 3/(4 + 3) = 3/7.

Hope it's clear.
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Guests at a recent party ate a total of fifteen hamburgers. [#permalink]
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Hi Math Experts, I have one question regarding my approach for this question:

This is a rule From MGMAT

If a Data Sufficiency question asks for the concrete value of one element of a ratio, you will need
BOTH the concrete value of another element of the ratio AND the relative value of two elements
of the ratio


So, after reading Statement 1, I've marked Answer A, because Statement 1 gives us the relationship among all the groups + we have a concrete value from the question stem, hence, one can find the required value --> I've just pretty much followed the rule from MGMAT....
Do you think it's a valid approach for such kind of questions ?
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Re: Guests at a recent party ate a total of fifteen hamburgers. [#permalink]
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I have outlined my approach in the attached file. Please share your thoughts about this approach. Thanks.
Attachments

vegnonveg.png
vegnonveg.png [ 49.54 KiB | Viewed 33204 times ]

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Re: Guests at a recent party ate a total of fifteen hamburgers. [#permalink]
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kairoshan wrote:
Guests at a recent party ate a total of fifteen hamburgers. Each guest who was neither a student nor a vegetarian ate exactly one hamburger. No hamburger was eaten by any guest who was a student, a vegetarian, or both. If half of the guests were vegetarians, how many guests attended the party?

(1) The vegetarians attended the party at a rate of 2 students to every 3 non-students, half the rate for non-vegetarians.

(2) 30% of the guests were vegetarian non-students.


The first step is to set up an overlapping sets table and insert the one known value: 15 non-vegetarian non-students. It's worded in a confusing way, but clearly the stimulus states that each relevant student at 1 hamburger each and only 15 hamburgers were eaten.

1) The ratio of vegetarian students to vegetarian non-students is 2:3, or half the ratio of non-vegetarians. So we know that non-vegetarians are in the ratio 4:3. 3x = 15, since we already know the number of non-vegetarian non-students, so x = 5. If x = 5, then the total number of vegetarians is 7(5) = 35. Since vegetarians are half of the guests, the total number of guests is 70. Sufficient.

2) This provides the relationship of the vegetarian non-student number to the total number of guests, but we don't know any other values. Not sufficient.
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Re: Guests at a recent party ate a total of fifteen hamburgers. [#permalink]
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main catch is 1 statement rate

Veg
2 student ---> 3 non student
1 s-------1.5 ns

half of it is for Non veg
1s-------1.5/2 ns

1s---------3/4 ns
4s => 3ns
4:3 ratio

=> 3x/7 = 15
x= 35
2x is total members => 70 is answer A.
since 2x are members x are veg and x are non veg
so took 4:3 s:ns for nonveg and since total number is x
so 3x/7 => x= 35 and 2x =70

and clearly 2 is insufficient
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