• Get 300+ Practice Questions

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

• Free Veritas GMAT Class
Experience Lesson 1 Live Free

Available with Beat the GMAT members only code

• 1 Hour Free
BEAT THE GMAT EXCLUSIVE

Available with Beat the GMAT members only code

• Free Trial & Practice Exam
BEAT THE GMAT EXCLUSIVE

Available with Beat the GMAT members only code

• Magoosh
Study with Magoosh GMAT prep

Available with Beat the GMAT members only code

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

Available with Beat the GMAT members only code

• 5 Day FREE Trial
Study Smarter, Not Harder

Available with Beat the GMAT members only code

• Most awarded test prep in the world
Now free for 30 days

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

## Vaccinated Against Rubella

tagged by: Brent@GMATPrepNow

This topic has 3 expert replies and 1 member reply
bml1105 Master | Next Rank: 500 Posts
Joined
24 Nov 2013
Posted:
113 messages
Followed by:
5 members
1

#### Vaccinated Against Rubella

Tue Jun 03, 2014 2:29 pm
In a certain region, the number of children who have been vaccinated against rubella is twice the number who have been vaccinated against mumps. The number who have been vaccinated against both is twice the number who have been vaccinated only against mumps. If 5,000 have been vaccinated against both, how many have been vaccinated only against rubella?

(A) 2,500
(B) 7,500
(C) 10,000
(D) 15,000
(E) 17,500

OA: C

### GMAT/MBA Expert

Jeff@TargetTestPrep GMAT Instructor
Joined
09 Apr 2015
Posted:
753 messages
Followed by:
11 members
39
Wed Nov 08, 2017 4:25 pm
bml1105 wrote:
In a certain region, the number of children who have been vaccinated against rubella is twice the number who have been vaccinated against mumps. The number who have been vaccinated against both is twice the number who have been vaccinated only against mumps. If 5,000 have been vaccinated against both, how many have been vaccinated only against rubella?

(A) 2,500
(B) 7,500
(C) 10,000
(D) 15,000
(E) 17,500
We can create the following formula:

Total = total mumps + total rubella - both + neither

We can let total mumps = m, and thus total rubella = 2m.

We can let both = b, and thus only mumps is m - b.

Since the number who have been vaccinated against both is twice the number who have been vaccinated only against mumps:

b = 2(m - b)

b = 2m - 2b

3b = 2m

Since b = 5000, we have:

3(5000) = 2m

15000 = 2m

7500 = m

Since m = 7500, the total number of children vaccinated against rubella is r = 2m = 2(7500) = 15000. Thus, the number who have been vaccinated against only rubella is r - b = 15000 - 5000 = 10000.

_________________
Jeffrey Miller Head of GMAT Instruction

### GMAT/MBA Expert

Brent@GMATPrepNow GMAT Instructor
Joined
08 Dec 2008
Posted:
11274 messages
Followed by:
1224 members
5254
GMAT Score:
770
Wed Jun 04, 2014 7:13 am
I thought I'd point out that Mitch's "group grid" (aka Double Matrix Method) can be used for most questions featuring a population in which each member has two characteristics associated with it.
Here, we have a population of children, and the two characteristics are:
- vaccinated against mumps or not vaccinated against mumps
- vaccinated against rubella or not vaccinated against rubella

This question type is VERY COMMON on the GMAT, so be sure to master the technique.

Once youâ€™re familiar with this technique, you can attempt these additional practice questions:

Easy Problem Solving questions
- http://www.beatthegmat.com/finance-majors-non-finance-majors-overlapping-set-question-t167425.html

Medium Problem Solving questions
- http://www.beatthegmat.com/probability-question-t273360.html
- http://www.beatthegmat.com/posted-speed-limit-t272374.html
- http://www.beatthegmat.com/motel-t271938.html
- http://www.beatthegmat.com/of-the-applicants-passes-a-certain-test-15-t270255.html
- http://www.beatthegmat.com/opening-night-and-late-patrons-t264869.html
- http://www.beatthegmat.com/ds-french-japanese-t222297.html

Difficult Problem Solving questions
- http://www.beatthegmat.com/ratio-problem-t268339.html
- http://www.beatthegmat.com/overlapping-sets-question-t265223.html
- http://www.beatthegmat.com/fractions-t264254.html
- http://www.beatthegmat.com/overlapping-sets-t264092.html
- http://www.beatthegmat.com/mba/2011/05/09/random-double-matrix-question-2

Easy Data Sufficiency questions
- http://www.beatthegmat.com/for-what-percent-of-those-tested-for-a-certain-t270596.html
- http://www.beatthegmat.com/ds-quest-t187706.html

Medium Data Sufficiency questions
- http://www.beatthegmat.com/sets-matrix-ds-t271914.html
- http://www.beatthegmat.com/each-of-people-voted-once-in-an-election-x-t271375.html
- http://www.beatthegmat.com/a-manufacturer-t270331.html
- http://www.beatthegmat.com/in-costume-for-halloween-t269355.html
- http://www.beatthegmat.com/mba/2011/05/05/random-double-matrix-question-1

Difficult Data Sufficiency questions
- http://www.beatthegmat.com/double-set-matrix-question-t271423.html
- http://www.beatthegmat.com/sets-t269449.html
- http://www.beatthegmat.com/mba/2011/05/16/random-double-matrix-question-3

Cheers,
Brent

_________________
Brent Hanneson â€“ Founder of GMATPrepNow.com
Use our video course along with

Check out the online reviews of our course
Come see all of our free resources

GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMATâ€™s FREE 60-Day Study Guide and reach your target score in 2 months!

### GMAT/MBA Expert

GMATGuruNY GMAT Instructor
Joined
25 May 2010
Posted:
13893 messages
Followed by:
1807 members
13060
GMAT Score:
790
Tue Jun 03, 2014 6:54 pm
Quote:
In a certain region, the number of children who have been vaccinated against rubella is twice the number who have been vaccinated against mumps. The number who have been vaccinated against both is twice the number who have been vaccinated only against mumps. If 5000 have been vaccinated against both, how many have been vaccinated only against rubella?

2500 : 7500 : 10000 : 15000 : 17500
This is an EITHER/OR group problem.
Every child EITHER has been vaccinated against mumps OR has not.
Every child EITHER has been vaccinated against rubella OR has not.
For an EITHER/OR group problem, we can use a GROUP GRID (also known as a double-matrix) to organize the data.

Let M = mumps, NM = not mumps, R = rubella, NR = not rubella.
In the grids below, the entries in any given row or column must add up to the TOTAL of that row or column.

The number who have been vaccinated against both is twice the number of who have been vaccinated against only mumps:

The number who have been vaccinated against rubella is twice the number who have been vaccinated against mumps:

5000 have been vaccinated against both:
According to the grid, both = 2x = 5000 and only rubella = 4x = 10,000.

_________________
Mitch Hunt
GMAT Private Tutor
GMATGuruNY@gmail.com
If you find one of my posts helpful, please take a moment to click on the "UPVOTE" 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.
GyanOne Master | Next Rank: 500 Posts
Joined
01 Dec 2011
Posted:
225 messages
Followed by:
9 members
16
Wed Jun 04, 2014 6:23 am
From the question statement, we can surmise:

Number vaccinated against both = 5000
Number vaccinated only against Mumps = 2500

Number vaccinated against mumps = Number vaccinated only against mumps + Number vaccinated against both = 5000 + 2500 = 7500

Number vaccinated against Rubella = 2 * 7500 = 15000

Number vaccinated against only Rubella = Number vaccinated against Rubella - Number vaccinated against both = 15000 - 5000 = 10,000

Option (C).

### Best Conversation Starters

1 lheiannie07 112 topics
2 ardz24 63 topics
3 LUANDATO 54 topics
4 Roland2rule 52 topics
5 swerve 47 topics
See More Top Beat The GMAT Members...

### Most Active Experts

1 GMATGuruNY

The Princeton Review Teacher

156 posts
2 Scott@TargetTestPrep

Target Test Prep

120 posts
3 Jeff@TargetTestPrep

Target Test Prep

106 posts
4 EconomistGMATTutor

The Economist GMAT Tutor

92 posts
5 Rich.C@EMPOWERgma...

EMPOWERgmat

91 posts
See More Top Beat The GMAT Experts