A group of 580 people participated in a survey. Each of these people indicated that they had either heard of brand A soda or had not heard of brand A soda, and each of these people indicated that they had either heard of brand B soda or had not heard of brand B soda. How many of the people surveyed indicated that they had heard of brand A soda and had not heard of brand B soda?
(1) There were 226 people who indicated that they had heard of exactly one of the two brands of soda.
(2) There were 187 people who indicated that they had not heard of either brand soda and there were 281 people who indicated that they had heard of brand B soda.
OA is B
I tried the overlapping set formula and chose C, but I guess that was unnecessary. Another explanation would be appreciated!
DS problem help!
This topic has expert replies
-
- Junior | Next Rank: 30 Posts
- Posts: 10
- Joined: Fri May 02, 2014 2:35 pm
- GMATGuruNY
- GMAT Instructor
- Posts: 15539
- Joined: Tue May 25, 2010 12:04 pm
- Location: New York, NY
- Thanked: 13060 times
- Followed by:1906 members
- GMAT Score:790
This is an EITHER/OR group problem.sdotgarcia wrote:A group of 580 people participated in a survey. Each of these people indicated that they had either heard of brand A soda or had not heard of brand A soda, and each of these people indicated that they had either heard of brand B soda or had not heard of brand B soda. How many of the people surveyed indicated that they had heard of brand A soda and had not heard of brand B soda?
(1) There were 226 people who indicated that they had heard of exactly one of the two brands of soda.
(2) There were 187 people who indicated that they had not heard of either brand soda and there were 281 people who indicated that they had heard of brand B soda.
OA is B
I tried the overlapping set formula and chose C, but I guess that was unnecessary. Another explanation would be appreciated!
Every person had EITHER heard of A OR had not heard of A.
Every person had EITHER heard of B OR had not heard of B.
For an EITHER/OR group problem, we can use a GROUP GRID (also known as a double-matrix) to organize the data:
In the grid above, the entries in any given row or column must add up to the TOTAL of that row or column.
The question stem asks for the number of people who had heard of A but had not heard of B (represented by the question mark).
Statement 1: There were 226 people who indicated that they had heard of exactly one of the two brands of soda.
Case 1:
In this case, the number of people who had heard of A but had not heard of B = 100.
Case 2:
In this case, the number of people who had heard of A but had not heard of B = 126.
Since the number of people who had heard of A but had not heard of B can be different values, INSUFFICIENT.
Statement 2: There were 187 people who indicated that they had not heard of either brand soda and there were 281 people who indicated that they had heard of brand B soda.
The following grid is yielded:
According to the resulting grid, the number of people who had heard of A but had not heard of B = 112.
SUFFICIENT.
The correct answer is B.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
-
- Junior | Next Rank: 30 Posts
- Posts: 10
- Joined: Fri May 02, 2014 2:35 pm
GMAT/MBA Expert
- Brent@GMATPrepNow
- 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
I thought I'd point out that Mitch's "group grid" approach (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 survey participants, and the two characteristics are:
- heard of brand A soda or not heard of brand A soda
- heard of brand B soda or not heard of brand B soda
This question type is VERY COMMON on the GMAT, so be sure to master the technique.
To learn more about the Double Matrix Method, watch our free video: https://www.gmatprepnow.com/module/gmat- ... ems?id=919
Once you're familiar with this technique, you can attempt these additional practice questions:
Easy Problem Solving questions
- https://www.beatthegmat.com/the-aam-aadm ... 72242.html
- https://www.beatthegmat.com/finance-majo ... 67425.html
Medium Problem Solving questions
- https://www.beatthegmat.com/probability- ... 73360.html
- https://www.beatthegmat.com/posted-speed ... 72374.html
- https://www.beatthegmat.com/motel-t271938.html
- https://www.beatthegmat.com/of-the-appli ... 70255.html
- https://www.beatthegmat.com/opening-nigh ... 64869.html
- https://www.beatthegmat.com/ds-french-ja ... 22297.html
Difficult Problem Solving questions
- https://www.beatthegmat.com/ratio-problem-t268339.html
- https://www.beatthegmat.com/overlapping- ... 65223.html
- https://www.beatthegmat.com/fractions-t264254.html
- https://www.beatthegmat.com/overlapping- ... 64092.html
- https://www.beatthegmat.com/mba/2011/05/ ... question-2
Easy Data Sufficiency questions
- https://www.beatthegmat.com/for-what-per ... 70596.html
- https://www.beatthegmat.com/ds-quest-t187706.html
Medium Data Sufficiency questions
- https://www.beatthegmat.com/sets-matrix-ds-t271914.html
- https://www.beatthegmat.com/each-of-peop ... 71375.html
- https://www.beatthegmat.com/a-manufacturer-t270331.html
- https://www.beatthegmat.com/in-costume-f ... 69355.html
- https://www.beatthegmat.com/mba/2011/05/ ... question-1
Difficult Data Sufficiency questions
- https://www.beatthegmat.com/double-set-m ... 71423.html
- https://www.beatthegmat.com/sets-t269449.html
- https://www.beatthegmat.com/mba/2011/05/ ... question-3
Here, we have a population of survey participants, and the two characteristics are:
- heard of brand A soda or not heard of brand A soda
- heard of brand B soda or not heard of brand B soda
This question type is VERY COMMON on the GMAT, so be sure to master the technique.
To learn more about the Double Matrix Method, watch our free video: https://www.gmatprepnow.com/module/gmat- ... ems?id=919
Once you're familiar with this technique, you can attempt these additional practice questions:
Easy Problem Solving questions
- https://www.beatthegmat.com/the-aam-aadm ... 72242.html
- https://www.beatthegmat.com/finance-majo ... 67425.html
Medium Problem Solving questions
- https://www.beatthegmat.com/probability- ... 73360.html
- https://www.beatthegmat.com/posted-speed ... 72374.html
- https://www.beatthegmat.com/motel-t271938.html
- https://www.beatthegmat.com/of-the-appli ... 70255.html
- https://www.beatthegmat.com/opening-nigh ... 64869.html
- https://www.beatthegmat.com/ds-french-ja ... 22297.html
Difficult Problem Solving questions
- https://www.beatthegmat.com/ratio-problem-t268339.html
- https://www.beatthegmat.com/overlapping- ... 65223.html
- https://www.beatthegmat.com/fractions-t264254.html
- https://www.beatthegmat.com/overlapping- ... 64092.html
- https://www.beatthegmat.com/mba/2011/05/ ... question-2
Easy Data Sufficiency questions
- https://www.beatthegmat.com/for-what-per ... 70596.html
- https://www.beatthegmat.com/ds-quest-t187706.html
Medium Data Sufficiency questions
- https://www.beatthegmat.com/sets-matrix-ds-t271914.html
- https://www.beatthegmat.com/each-of-peop ... 71375.html
- https://www.beatthegmat.com/a-manufacturer-t270331.html
- https://www.beatthegmat.com/in-costume-f ... 69355.html
- https://www.beatthegmat.com/mba/2011/05/ ... question-1
Difficult Data Sufficiency questions
- https://www.beatthegmat.com/double-set-m ... 71423.html
- https://www.beatthegmat.com/sets-t269449.html
- https://www.beatthegmat.com/mba/2011/05/ ... question-3