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

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Joined: 04 Jan 2015
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Re: Of the 84 parents who attended a meeting at a school, 35  [#permalink]

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07 May 2015, 09:32
1
1
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]

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31 May 2015, 14:18
2
Given:

{Total} = {Supervise} + {Refreshments} - {Both} + {Neither}

Given:

{Refreshments} = 1.5 {Neither}

Calculations:

84 = 35 + 1.5 {Neither} - 11 + {Neither}

84 + 11 - 35 = 2.5 {Neither}

60 = 2.5 {Neither}

{Neither} = 24

{Refreshments} = 1.5 {Neither} = 1.5 {24} = 36
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Of the 84 parents who attended a meeting at a school, 35  [#permalink]

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02 Jun 2015, 08:26
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?

Let's say that a = supervise group, b = supervise and refreshment group c = neither
a + b + c = 84
b = ?

a is 35 - 11 = 24 (We subtract so as not to double count those who volunteered for both)
24 + b + c = 84 => b + c = 60
=> c = 60 - b

We're told that b = 1.5c. You can substitute for c.
b = 1.5 (60-b) => 90 - 1.5b
2.5b = 90
b = 36

A) 25
B) 36
C) 38
D) 42
E) 45
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Re: Of the 84 parents who attended a meeting at a school, 35  [#permalink]

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20 Dec 2015, 09:30
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?!?!

I find it easier to write the given info in the following manner:

N (Neither) -parents who will not be supervising or bringing refreshments
S (Supervising) - parents who will be only supervising
R (Refreshments) - parents who will bring refreshments only
R=1.5N

Step 1.
We know that total number of parents is 84, which is N+S+R, to find N ==>
N= 84-S-R, where S = 35-11=24
N=84-24-R
N=60-R, we already know that R=1.5N, substitute to get ==>
N=60-1.5N
2.5N=60
N=24 (24 parents will not be supervising or bringing refreshments)

Step 2.
R=1.5N, substitute to get==>
R=1.5*24
R=36 (parents will bring refreshments!!!)
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Of the 84 parents who attended a meeting at a school, 35  [#permalink]

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17 Feb 2016, 23:47
This question's difficulty level would have jumped an extra 50 points if it had 24 as an answer choice.
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Re: Of the 84 parents who attended a meeting at a school, 35  [#permalink]

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12 Sep 2016, 12:09
A = Supervising Children only
B = Both
C = Bring refreshments only
X = Neither

A + B = 35
B = 11
A = 24
B + C = 1.5X
A +B + C + x = 84 (total)

24 + 1.5x + x = 84
2.5x = 60
x = 24
1.5x = 36

Option B
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Re: Of the 84 parents who attended a meeting at a school, 35  [#permalink]

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06 Oct 2017, 09:57
Bunuel wrote:
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

We can use the following formula:

Total = Picnic + Refreshment - Both + Neither

We are given that Total = 84, Picnic = 35, Both = 11, and Refreshment = 1.5 x Neither. Thus, if we let n = Neither, we have:

84 = 35 + 1.5n - 11 + n

84 = 24 + 2.5n

60 = 2.5n

n = 60/2.5 = 600/25 = 24

Since Refreshment = 1.5 x Neither, Refreshment = 1.5 x 24 = 36.

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Re: Of the 84 parents who attended a meeting at a school, 35  [#permalink]

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09 Aug 2018, 06:30
Total - neither = Supervise + Refreshment - Both
Total = 84
Neither = N
Supervise = 35
Refreshment = 1.5N
Both = 11

84-N = 35+1.5N-11
2.5N = 60
N=24

Refreshment = 24*1.5 = 36
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Re: Of the 84 parents who attended a meeting at a school, 35  [#permalink]

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09 Aug 2018, 22:29
As with many GMAT questions, there are many ways to arrive at the answer to this question! I am adding my two cents as part of my new project to go through all of the Quant questions in the 2019 Official Guide and share my suggested "GMAT Timing Tips" for each one: that is, what could you notice or do to be able to answer each question more efficiently? For this question, my GMAT Timing Tips are:

Two-set Venn Diagrams: Draw out the Venn Diagram to quickly see how the numbers you are given relate to what you are asked to calculate. As many people have done on this thread, you can find that 24 parents volunteered only to supervise children.
Use smart variables to represent unknowns: I recommend using the variable R to represent the total number of parents who volunteered to bring refreshments, because that is what the question asks us to solve for. Then, using the Venn Diagram and the information in the question, write the equation R = 1.5(84 - 24 - R), and just solve for R.

I'm also planning to create video solutions demonstrating how to use my GMAT Timing Tips for each of the Official Guide Quant questions. This will take a while, but I'll start with the those that I get requests for first. If you would me to create a video solution for this question, please go to the page that I have created for this question and vote for or share it: Of the 84 parents who attended a meeting at a school, 35..

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Re: Of the 84 parents who attended a meeting at a school, 35  [#permalink]

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15 Oct 2018, 15:08
Bunuel wrote:
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

Attachments

File comment: ATTACHED is the solution :) I hope you like it...

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Screen Shot 2018-10-15 at 6.07.07 PM.png [ 566.88 KiB | Viewed 1147 times ]

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Re: Of the 84 parents who attended a meeting at a school, 35  [#permalink]

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08 Dec 2018, 13:35
Hi everyone,

I understand the math behind this question, however I am struggling with one particular part of the problem. In the opening statement, "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." What part clues you into the fact that you need to subtract the intersection of the set of parents that supervised and the set that supervised and brought refreshments?

How do I know that the 11 parents are certainly the intersection of the parents who brought drinks and the parents who supervised? How would I know that we are not dealing with three independent sets?
Intern
Joined: 07 May 2019
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Of the 84 parents who attended a meeting at a school, 35  [#permalink]

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25 Jun 2019, 09:01
I'm sorry for the stupid questions but anyway:

1.
Quote:
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

Why it's not 1.5 * (84-35)

2.
Quote:
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.

In official guide solution: 35-11?
But I read it like 35 and 11 but not 11 among 35
What's the trick?
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Of the 84 parents who attended a meeting at a school, 35  [#permalink]

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28 Dec 2019, 16:21

Hi Experts --

My mistake was I was got the two MECE groups completely incorrect

Any suggestion on how to determine the two MECE groups accurately with so MUCH verbiage

- Volunteer
- Not Volunteer
- Bring refreshments
- Dont bring refreshments

Given my MECE groups were wrong -- i could not interpret the question accurately and thus bailed on this one

Any suggestions / tips on avoiding picking up the wrong MECE group/ s when there is so much text ?
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Re: Of the 84 parents who attended a meeting at a school, 35  [#permalink]

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03 Jul 2020, 03:43
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Re: Of the 84 parents who attended a meeting at a school, 35   [#permalink] 03 Jul 2020, 03:43

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