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Of the 84 parents who attended a meeting at a school, 35

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Of the 84 parents who attended a meeting at a school, 35 [#permalink]  02 Jul 2012, 01:18
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Difficulty:

55% (hard)

Question Stats:

68% (03:28) correct 32% (02:53) wrong based on 406 sessions
Of the 84 parents who attended a meeting at a school, 35 volunteered to supervise children during the school picnic and 11 volunteered both to supervise children during the picnic and to bring refreshments to the picnic. If the number of parents who volunteered to bring refreshments was 1.5 times the number of parents who neither volunteered to supervise children during the picnic nor volunteered to bring refreshments, how many of the parents volunteered to bring refreshments?

(A) 25
(B) 36
(C) 38
(D) 42
(E) 45

Diagnostic Test
Question: 14
Page: 22
Difficulty: 650
[Reveal] Spoiler: OA

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Re: Of the 84 parents who attended a meeting at a school, 35 [#permalink]  02 Jul 2012, 01:19
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SOLUTION

Of the 84 parents who attended a meeting at a school, 35 volunteered to supervise children during the school picnic and 11 volunteered both to supervise children during the picnic and to bring refreshments to the picnic. If the number of parents who volunteered to bring refreshments was 1.5 times the number of parents who neither volunteered to supervise children during the picnic nor volunteered to bring refreshments, how many of the parents volunteered to bring refreshments?

(A) 25
(B) 36
(C) 38
(D) 42
(E) 45

Look at the matrix below:

Notice that numbers in black are given and in red are calculated. We need the value of yellow box: $$1.5x+(24+x)=84$$ --> $$x=24$$ --> $$1.5x=36$$.

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Re: Of the 84 parents who attended a meeting at a school, 35 [#permalink]  02 Jul 2012, 02:11
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Total = 84
who volunteered for picnic = 35
who volunteered for picnic & refr = 11
then -who opt picnic but not refreshmnt = 24
the no. of parents who didnt volunteer for picnic and refesh = x
the no. who volunteer for refreshmnt = 1.5 x

1.5x + 24 = 35
x= 24
1.5x = 36

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Re: Of the 84 parents who attended a meeting at a school, 35 [#permalink]  02 Jul 2012, 02:37
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Quote:
Of the 84 parents who attended a meeting at a school, 35 volunteered to supervise children during the school picnic and 11 volunteered both to supervise children during the picnic and to bring refreshments to the picnic. If the number of parents who volunteered to bring refreshments was 1.5 times the number of parents who neither volunteered to supervise children during the picnic nor volunteered to bring refreshments, how many of the parents volunteered to bring refreshments?

(A) 25
(B) 36
(C) 38
(D) 42
(E) 45

Hi,

Difficulty level: 600

let, number of parents who neither bring refreshment nor supervise = x
Attachment:

venn2.jpg [ 11.03 KiB | Viewed 4895 times ]

then,
35-11+1.5x+x=84
x = 24
or Parents who bring refreshment = 1.5x = 36

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Last edited by cyberjadugar on 09 Jul 2012, 00:00, edited 1 time in total.
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Re: Of the 84 parents who attended a meeting at a school, 35 [#permalink]  06 Jul 2012, 02:05
Expert's post
SOLUTION

Of the 84 parents who attended a meeting at a school, 35 volunteered to supervise children during the school picnic and 11 volunteered both to supervise children during the picnic and to bring refreshments to the picnic. If the number of parents who volunteered to bring refreshments was 1.5 times the number of parents who neither volunteered to supervise children during the picnic nor volunteered to bring refreshments, how many of the parents volunteered to bring refreshments?

(A) 25
(B) 36
(C) 38
(D) 42
(E) 45

Look at the matrix below:
Attachment:

OG.PNG [ 5.62 KiB | Viewed 4875 times ]
Notice that numbers in black are given and in red are calculated. We need the value of yellow box: $$1.5x+(24+x)=84$$ --> $$x=24$$ --> $$1.5x=36$$.

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Re: Of the 84 parents who attended a meeting at a school, 35 [#permalink]  22 Jun 2014, 06:16
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Of the 84 parents who attended a meeting at a school, 35 [#permalink]  23 Jun 2014, 00:00
Refer diagram below

We require to find x (Red shaded region)

$$35 + x - 11 + \frac{10x}{15} = 84$$

x = 36

Attachments

venn2.jpg [ 27.56 KiB | Viewed 2220 times ]

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Re: Of the 84 parents who attended a meeting at a school, 35 [#permalink]  09 Jul 2014, 08:33
kashishh wrote:
Total = 84
who volunteered for picnic = 35
who volunteered for picnic & refr = 11
then -who opt picnic but not refreshmnt = 24
the no. of parents who didnt volunteer for picnic and refesh = x
the no. who volunteer for refreshmnt = 1.5 x

1.5x + 24 = 35
x= 24
1.5x = 36

Hi
the no. who volunteer for refreshmnt = 1.5 x
but no. who did refreshment but not picnic = 1.5x- 11????? why we don't apply this step just like we did for picnic numbers???

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Re: Of the 84 parents who attended a meeting at a school, 35 [#permalink]  09 Jul 2014, 17:33
GGMAT760 wrote:
kashishh wrote:
Total = 84
who volunteered for picnic = 35
who volunteered for picnic & refr = 11
then -who opt picnic but not refreshmnt = 24
the no. of parents who didnt volunteer for picnic and refesh = x
the no. who volunteer for refreshmnt = 1.5 x

1.5x + 24 = 35
x= 24
1.5x = 36

Hi
the no. who volunteer for refreshmnt = 1.5 x
but no. who did refreshment but not picnic = 1.5x- 11????? why we don't apply this step just like we did for picnic numbers???

Hope I got the question right

11 (who volunteered for picnic & refr) is common in both. So it has to be subtracted from ANY ONE
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Re: Of the 84 parents who attended a meeting at a school, 35 [#permalink]  06 May 2015, 18:28
This question is confusing me so if anyone could explain in detail I would really appreciate it. I don't understand why it isn't solved the same way as practice question 6... in that question you had Brand A + Brand B + both brands + neither brands = 200 and the answer was 15... on this question though, it is leaving out AND part (11) out of the results. Why isn't it 24 + 1.5x + 11 + × = 84?!?!
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Re: Of the 84 parents who attended a meeting at a school, 35 [#permalink]  07 May 2015, 00:38
danepenell wrote:
This question is confusing me so if anyone could explain in detail I would really appreciate it. I don't understand why it isn't solved the same way as practice question 6... in that question you had Brand A + Brand B + both brands + neither brands = 200 and the answer was 15... on this question though, it is leaving out AND part (11) out of the results. Why isn't it 24 + 1.5x + 11 + × = 84?!?!

Hi danepenell

Please post practice question 6 (or the link for it) here and I'll be happy to help with your doubt.
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Re: Of the 84 parents who attended a meeting at a school, 35 [#permalink]  07 May 2015, 01:44
Expert's post
danepenell wrote:
This question is confusing me so if anyone could explain in detail I would really appreciate it. I don't understand why it isn't solved the same way as practice question 6... in that question you had Brand A + Brand B + both brands + neither brands = 200 and the answer was 15... on this question though, it is leaving out AND part (11) out of the results. Why isn't it 24 + 1.5x + 11 + × = 84?!?!

It's {Group 1} + {Group 1} - {Both} + {Neither} = {Total}

You CAN solve this problem with this formula:
{refreshments} + {supervise} - {both} + {Neither} = {Total}

35 + 1.5x - 11 + x = 84
x = 24.
1.5x = 36.

Hope it helps.

P.S. Practice question 6 is here: of-the-84-parents-who-attended-a-meeting-at-a-school-135191.html
All OG13 questions are here: the-official-guide-quantitative-question-directory-143450.html
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Re: Of the 84 parents who attended a meeting at a school, 35 [#permalink]  07 May 2015, 09:32
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danepenell wrote:
This question is confusing me so if anyone could explain in detail I would really appreciate it. I don't understand why it isn't solved the same way as practice question 6... in that question you had Brand A + Brand B + both brands + neither brands = 200 and the answer was 15... on this question though, it is leaving out AND part (11) out of the results. Why isn't it 24 + 1.5x + 11 + × = 84?!?!

Hi danepenell,

The underlying concept behind both the questions is the same. However, there is slight change in the way the information has been provided. Let me explain with a venn diagram.

In the questions with two overlapping sets a + b + c + d = Total no. of objects. In both the questions, the same concept has been used.

However there is a difference between the way information has been provided. Let's see how.

In this question let's assume group 1 = parents who volunteer to supervise children and group 2 =parents who bring refreshements

The question gives us the value of no. of parents who volunteer to supervise children = 35. Please note that this includes parents who only supervise children as well as parents who supervise children and bring refreshments both. So, a + b = 35. Also, parents who volunteer to supervise children as well as bring refreshment = b = 11. So, we can write the value of a = 24.

Since we are also told that no. of parents who volunteered to bring refreshment is 1.5 times the no. of parents who neither volunteered to supervise children nor bring refreshment, we can write b + c = 1.5d. Note here that parents who volunteered to bring refreshments include parents who only bring refreshments as well as parents who bring refreshments and supervise children both.

Since a + b + c + d = Total number of parents = 84, we can write 24 + (b + c) + d = 84. Since b + c = 1.5d, 24 + 2.5d = 84 which gives us the value of d = 24 and hence b + c = 1.5*24 = 36.

For every set question, please keep an eye on the use of word "Only". In this case the question asked the number of parents who volunteered to bring refreshments which also included parents who volunteered to supervise the children as well as bring refreshments.

In practice question no. 6, note the use of word "Only". The question there uses the term extensively to segregate the users of the brands. For your reference, in Q6 we can write the value of a = 60, b = x, c = 3x and d = 80 assuming group 1 as users of brand A and group 2 as users of brand B.

Hope its clear! Let me know if you still have trouble at any point of the explanation.

Regards
Harsh
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Re: Of the 84 parents who attended a meeting at a school, 35   [#permalink] 07 May 2015, 09:32
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