• 5-Day Free Trial
5-day free, full-access trial TTP Quant

Available with Beat the GMAT members only code

• Free Trial & Practice Exam
BEAT THE GMAT EXCLUSIVE

Available with Beat the GMAT members only code

• Free Practice Test & Review
How would you score if you took the GMAT

Available with Beat the GMAT members only code

• 1 Hour Free
BEAT THE GMAT EXCLUSIVE

Available with Beat the GMAT members only code

• Award-winning private GMAT tutoring
Register now and save up to \$200

Available with Beat the GMAT members only code

• 5 Day FREE Trial
Study Smarter, Not Harder

Available with Beat the GMAT members only code

• Get 300+ Practice Questions

Available with Beat the GMAT members only code

• Magoosh
Study with Magoosh GMAT prep

Available with Beat the GMAT members only code

• Free Veritas GMAT Class
Experience Lesson 1 Live Free

Available with Beat the GMAT members only code

## Problem Solving on Set Theory

This topic has 2 expert replies and 1 member reply
mohaprasad Newbie | Next Rank: 10 Posts
Joined
02 Feb 2014
Posted:
2 messages

#### Problem Solving on Set Theory

Wed Feb 19, 2014 4:53 pm
Elapsed Time: 00:00
• Lap #[LAPCOUNT] ([LAPTIME])
Hello,

Could you please assist me with the below question.
The below question is from OG13 diagnostic test Q14.

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 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

Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
tomada Master | Next Rank: 500 Posts
Joined
25 Jan 2010
Posted:
406 messages
Followed by:
4 members
Thanked:
23 times
Test Date:
March 14, 2014
GMAT Score:
740
Wed Feb 19, 2014 6:13 pm
Hello,

Could you please assist me with the below question.
The below question is from OG13 diagnostic test Q14.

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 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
Looks like this question has been floating around the internet for a while. The following page contains a good explanation for how to solve this problem.

http://gmatclub.com/forum/of-the-84-parents-who-attended-a-meeting-at-a-school-35-volunteered-111450.html

_________________
I'm really old, but I'll never be too old to become more educated.

### GMAT/MBA Expert

Patrick_GMATFix GMAT Instructor
Joined
21 May 2010
Posted:
1053 messages
Followed by:
97 members
Thanked:
334 times
Thu Feb 20, 2014 12:51 am
This is a great question; the full solution below is taken from the GMATFix App (QID 8412).

-Patrick

_________________

### GMAT/MBA Expert

GMATGuruNY GMAT Instructor
Joined
25 May 2010
Posted:
13352 messages
Followed by:
1779 members
Thanked:
12877 times
GMAT Score:
790
Thu Feb 20, 2014 3:55 am
Hello,

Could you please assist me with the below question.
The below question is from OG13 diagnostic test Q14.

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 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
Total = Group 1 + Group 2 - Both + Neither.

The big idea with overlapping groups is the SUBTRACT THE OVERLAP.
When we count everyone in Group 1 (those who volunteer to supervise) and everyone in Group 2 (those who volunteer to bring refreshments), those in BOTH groups (those who volunteer to do both) are counted TWICE.
Thus, we SUBTRACT THE OVERLAP -- the number in both groups -- so that these people are not double-counted.

In the problem above:
Total = 84.
Group 1 = Supervise = 35.
Both = 11.
Neither = x.
Since the number of parents who volunteered to bring refreshments was 1.5 times the number of parents who neither volunteered to supervise during the picnic nor volunteered to bring refreshments:
Group 2 = Refreshments = 1.5x.

Plugging these values into the formula, we get:

84 = 35 + 1.5x - 11 + x
84 = 24 + 2.5x
x = 60/(2.5) = 600/25 = 24.

Thus:
Refreshments = (1.5)x = (1.5)(24) = 36.

_________________
Mitch Hunt
GMAT Private Tutor
GMATGuruNY@gmail.com
If you find one of my posts helpful, please take a moment to click on the "Thank" icon.
Available for tutoring in NYC and long-distance.

Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.

### Best Conversation Starters

1 Vincen 180 topics
2 lheiannie07 61 topics
3 Roland2rule 54 topics
4 ardz24 44 topics
5 VJesus12 14 topics
See More Top Beat The GMAT Members...

### Most Active Experts

1 Brent@GMATPrepNow

GMAT Prep Now Teacher

155 posts
2 Rich.C@EMPOWERgma...

EMPOWERgmat

105 posts
3 GMATGuruNY

The Princeton Review Teacher

101 posts
4 Jay@ManhattanReview

Manhattan Review

82 posts
5 Matt@VeritasPrep

Veritas Prep

80 posts
See More Top Beat The GMAT Experts