Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 350,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

A research study found that, of 500 people surveyed, 220 [#permalink]
06 Mar 2013, 18:37

2

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

15% (low)

Question Stats:

71% (02:15) correct
29% (01:00) wrong based on 118 sessions

A research study found that, of 500 people surveyed, 220 watched neither Network A nor Network B, 120 watched only Network A, and for every person who watched both networks, 3 watched only Network B. How many of the 500 people surveyed watched both networks?

(A) 40 (B) 60 (C) 80 (D) 100 (E) 120

I always screw up with the correct usage of this relationship: [Total = Group1 + Group2 - Both + Neither] vs [Total = Group1 + Group2 + Both + Neither], i.e. when to subtract Both and when to add Both

Re: A research study found that, of 500 people surveyed, 220 [#permalink]
06 Mar 2013, 19:53

1

This post received KUDOS

1

This post was BOOKMARKED

megafan, see the attached figure.

the portion in green corresponds to neither A nor B. The one in brown corresponds to only A. The one in blue to only B. The one in red to both A and B.

n(Total) = n(Neither A nor B) + n(only A) + n(only B) + n(both A and B) => 500 = 220 + 120 + 3x + x => x = 160/4 = 40

Re: A research study found that, of 500 people surveyed, 220 [#permalink]
06 Mar 2013, 20:51

2

This post received KUDOS

Expert's post

Here are the two formulas

1. [Total = Group1 + Group2 - Both + Neither]

Used when Group1 includes Both. e.g. given 160 people watch network A. This means 160 watch network A and it includes those people who watch both the networks. Similarly, Group2 includes people who watch both the networks e.g. given 160 watch network B - 160 includes the number of people who watch both networks. Since no of people who watch both networks is included twice, you subtract it out once.

500 = 160 + 160 - 40 + 220

2. [Total = Group1 + Group2 + Both + Neither]

Used when Group1 is the number of people who watch ONLY network A e.g. given 120 people watch ONLY network A (compare this with above where the word ONLY is missing). Group2 includes people who watch ONLY network B. Since you haven't accounted for the people who watch both, you add Both once.

500 = 120 + 120 + 40 + 220

Hope both the formulas make sense now.

Here, you are given that 120 watched only network A so you use the second formula. Also, it might be a good idea to get comfortable with venn diagrams. Such confusions do not occur if you always use the venn diagram. _________________

Re: A research study found that, of 500 people surveyed, 220 [#permalink]
07 Mar 2013, 00:52

1

This post received KUDOS

Expert's post

megafan wrote:

A research study found that, of 500 people surveyed, 220 watched neither Network A nor Network B, 120 watched only Network A, and for every person who watched both networks, 3 watched only Network B. How many of the 500 people surveyed watched both networks?

(A) 40 (B) 60 (C) 80 (D) 100 (E) 120

I always screw up with the correct usage of this relationship: [Total = Group1 + Group2 - Both + Neither] vs [Total = Group1 + Group2 + Both + Neither], i.e. when to subtract Both and when to add Both

Re: A research study found that, of 500 people surveyed, 220 [#permalink]
07 Mar 2013, 08:08

VeritasPrepKarishma wrote:

Here are the two formulas

1. [Total = Group1 + Group2 - Both + Neither]

Used when Group1 includes Both. e.g. given 160 people watch network A. This means 160 watch network A and it includes those people who watch both the networks. Similarly, Group2 includes people who watch both the networks e.g. given 160 watch network B - 160 includes the number of people who watch both networks. Since no of people who watch both networks is included twice, you subtract it out once.

500 = 160 + 160 - 40 + 220

2. [Total = Group1 + Group2 + Both + Neither]

Used when Group1 is the number of people who watch ONLY network A e.g. given 120 people watch ONLY network A (compare this with above where the word ONLY is missing). Group2 includes people who watch ONLY network B. Since you haven't accounted for the people who watch both, you add Both once.

500 = 120 + 120 + 40 + 220

Hope both the formulas make sense now.

Here, you are given that 120 watched only network A so you use the second formula. Also, it might be a good idea to get comfortable with venn diagrams. Such confusions do not occur if you always use the venn diagram.

Wow, thanks a lot! This makes the problem seem like a 300-level question. I think I usually don't pay attention to the elements in the set -- i.e. whether there is an overlap or not. Note to self: watch out for only. _________________

Re: A research study found that, of 500 people surveyed, 220 [#permalink]
08 Mar 2013, 23:32

Expert's post

skiingforthewknds wrote:

and for every person who watched both networks, 3 watched only Network B. How many of the 500 people surveyed watched both networks?

Can someone clarify this wording? I understood what they were testing but I couldn't figure out what that meant....

It just gives you the relation between the two groups:

- No of people who watched both networks - No of people who watched only network B

It means that if there is only 1 person who watches both networks, there are 3 who watch only network B. If there are 2 people who watch both networks, there are 6 who watch only network B and so on... It is just another way of telling that the ratio of no of people watching both networks and no of people who watch only network B is 1:3

So if x people watch both networks, 3x watch only network B. _________________

Re: A research study found that, of 500 people surveyed, 220 [#permalink]
29 May 2013, 14:09

1

This post received KUDOS

Expert's post

piyushdiyora wrote:

Can anyone solve the same problem using 2 way matrix

A research study found that, of 500 people surveyed, 220 watched neither Network A nor Network B, 120 watched only Network A, and for every person who watched both networks, 3 watched only Network B. How many of the 500 people surveyed watched both networks? (A) 40 (B) 60 (C) 80 (D) 100 (E) 120

Re: A research study found that, of 500 people surveyed, 220 [#permalink]
19 Jun 2014, 07:07

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________

Social entrepreneurs aren't running charities : ‘It’s easy to think about it in terms of charity: it’s not. They are sustainable, trading, revenue-generating businesses. The benefit of them...