BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Sets problem

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Legendary Member
Posts: 1893
Joined: Sun May 30, 2010 11:48 pm
Thanked: 215 times
Followed by:7 members

Sets problem

by kvcpk » Sat Jun 05, 2010 2:47 am
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

Can someone please explain me the soluton. I think that the OG's solution is wrong. this is review problem from OG12.

OA is B
Top
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 1179
Joined: Sun Apr 11, 2010 9:07 pm
Location: Milpitas, CA
Thanked: 447 times
Followed by:88 members

by Rahul@gurome » Sat Jun 05, 2010 3:04 am
Let the number of parents who volunteered to bring refreshments only be x.
Let the number of parents who neither volunteered to supervise children nor volunteered to bring refreshments be y.
It is given that 11 parents volunteered to both supervise children and bring refreshments.
So 11+x parents volunteered to bring refreshments.
So 11+x = 1.5y.
Also 35+x+y = 84.
From this we have y = 24.
So 1.5y = 36.
Or 11+x = 36.
Or numbrer of parents who volunteered to bring refreshments is 36.

The correct answer is (B).
Rahul Lakhani
Quant Expert
Gurome, Inc.
https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
1-800-566-4043 (USA)
+91-99201 32411 (India)
Top
User avatar
Legendary Member
Posts: 1893
Joined: Sun May 30, 2010 11:48 pm
Thanked: 215 times
Followed by:7 members

by kvcpk » Sat Jun 05, 2010 3:22 am
Rahul@gurome wrote:Let the number of parents who volunteered to bring refreshments only be x.
Let the number of parents who neither volunteered to supervise children nor volunteered to bring refreshments be y.
It is given that 11 parents volunteered to both supervise children and bring refreshments.
So 11+x parents volunteered to bring refreshments.
So 11+x = 1.5y.
Also 35+x+y = 84.
From this we have y = 24.
So 1.5y = 36.
Or 11+x = 36.
Or numbrer of parents who volunteered to bring refreshments is 36.

The correct answer is (B).
Thanks for your prompt response. I was doing the same but got confused with OG's solution. Your solution seems more convincing.
Top
Senior | Next Rank: 100 Posts
Posts: 85
Joined: Sat Aug 15, 2009 4:36 am
Thanked: 19 times

by gmatjedi » Sat Jun 05, 2010 4:02 am
x=refreshments only

x+11=1.5[84-35-x]
x=25

refreshments =25+11=36
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

Re: Sets problem

by Brent@GMATPrepNow » Sun Jan 19, 2020 12:32 pm
kvcpk wrote: ↑
Sat Jun 05, 2010 2:47 am
 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

Can someone please explain me the soluton. I think that the OG's solution is wrong. this is review problem from OG12.

OA is B
One approach is to use the Double Matrix Method. This technique can be used for most questions featuring a population in which each member has two characteristics associated with it (aka overlapping sets questions).
Here, we have a population of baseball players, and the two characteristics are:
- supervised children or did not supervise children
- bring refreshments or didn't bring refreshments

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.
So, we get the following:
Image

The number of parents who volunteered to bring refreshments was 1.5 times the number of parents who neither volunteered to supervise children during picnic nor volunteered to bring refreshments
If we let x = the number of parents who neither supervised not brought refreshments, then
1.5x = the number of parents who brought refreshments
Image


How many of the parents volunteered to bring refreshments?
In other words, what is the value of 1.5x?
Notice that, if we add the two boxes in the right-hand column, then we see that 24+x = the total number of parents who DIDN'T bring refreshments.
Image

At this point, we know that 1.5x = the number of parents who brought refreshments, and 24+x = the number of parents who DIDN'T bring refreshments.
We can write: 1.5x + (24 + x) = 84 (the total number of parents)
Simplify: 2.5x + 24 = 84
2.5x = 60
x = 24

We already know that 1.5x = the number of parents who brought refreshments
1.5(24) = 36
So, 36 parents brought refreshments

Answer: B
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 8086
Joined: Sat Apr 25, 2015 10:56 am
Location: Los Angeles, CA
Thanked: 43 times
Followed by:29 members

Re: Sets problem

by Scott@TargetTestPrep » Thu Jan 23, 2020 11:05 am
kvcpk wrote: ↑
Sat Jun 05, 2010 2:47 am
 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

Can someone please explain me the soluton. I think that the OG's solution is wrong. this is review problem from OG12.

OA is B
Solution:

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, then Refreshment = 1.5 x 24 = 36.

Answer: B

Scott Woodbury-Stewart
Founder and CEO
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

ImageImage
Top
Post new topic Post Reply
• Page 1 of 1