It is currently 15 Jan 2018, 23:59

Close

GMAT Club Daily Prep

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.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Of the 300 subjects who participated in an experiment using

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Intern
Intern
avatar
B
Joined: 02 Nov 2017
Posts: 6

Kudos [?]: 0 [0], given: 8

Re: Of the 300 subjects who participated in an experiment using [#permalink]

Show Tags

New post 14 Dec 2017, 03:49
geometric wrote:
The best way to tackle this question is probably the formula for three overlapping sets:

Total = Group1 + Group 2 + Group 3 - (sum of 2-group overlaps) - 2*(all three) + Neither

Total = 300(.4) + 300(.3) + 300(.75) - 300(.35) - 2*(all three) + 0
300*.1 = 30
300 = 120 + 90 + 225 - 105 - 2*(all three)
2*(all three) = 30
:. 15 experienced all three effects

So Group 1 + Group 2 + Group 3 - 2-group overlaps * 2 - 3-group overlaps * 3 is our answer
= 120 + 90 + 225 - 105*2 - 15*3
= 435 - 210 - 45
= 180



I did not understand the 2nd part of the answer. how did you derive this formula and when is it supposed to be used? Any help would be appreciated.

Kudos [?]: 0 [0], given: 8

Intern
Intern
avatar
B
Joined: 30 Jan 2017
Posts: 3

Kudos [?]: 0 [0], given: 0

Of the 300 subjects who participated in an experiment using [#permalink]

Show Tags

New post 01 Jan 2018, 23:47
N(a U b U c) = N(a) + N(b) + N(c) - N(a ∩ b) - N(b ∩ c) - N(c ∩ a) + N(a ∩ b ∩ c)

N(a ∩ b) = (only a, b) + N(a ∩ b ∩ c)
N(c ∩ b) = (only c, b) + N(a ∩ b ∩ c)
N(a ∩ c) = (only c, a) + N(a ∩ b ∩ c)

In percentages:
100 = 40+30+75-35-2N(a ∩ b ∩ c) ----> N(a ∩ b ∩ c) = 5

100 = (exactly one) + (exactly two) + (exactly three) ---> exactly one = 100-35-5 ---> exactly one = 60% ---> 180 people

Hence answer: D

Kudos [?]: 0 [0], given: 0

Manager
Manager
User avatar
B
Joined: 09 Mar 2016
Posts: 132

Kudos [?]: 23 [0], given: 179

Re: Of the 300 subjects who participated in an experiment using [#permalink]

Show Tags

New post 02 Jan 2018, 09:23
Bunuel wrote:
iwillbeatthegmat wrote:
vandygrad11 wrote:
The best way to tackle this question is probably the formula for three overlapping sets:

Total = Group1 + Group 2 + Group 3 - (sum of 2-group overlaps) - 2*(all three) + Neither

Total = 300(.4) + 300(.3) + 300(.75) - 300(.35) - 2*(all three) + 0
300*.1 = 30
300 = 120 + 90 + 225 - 105 - 2*(all three)
2*(all three) = 30
:. 15 experienced all three effects

So Group 1 + Group 2 + Group 3 - 2-group overlaps * 2 - 3-group overlaps * 3 is our answer
= 120 + 90 + 225 - 105*2 - 15*3
= 435 - 210 - 45
= 180


I'm having trouble understanding this formula. Why is the sum of all three overlaps multiplied by two?

Thanks in advance.


Explained here: http://gmatclub.com/forum/advanced-over ... 44260.html

Hope it helps.


Hello Bunuel, can you please explain this 2*(all three) how do we get 15*3 ? I checked the link you provided, but still cant understand this moment. :? thank you :-)

Kudos [?]: 23 [0], given: 179

Manager
Manager
User avatar
B
Joined: 09 Mar 2016
Posts: 132

Kudos [?]: 23 [0], given: 179

Re: Of the 300 subjects who participated in an experiment using [#permalink]

Show Tags

New post 02 Jan 2018, 14:13
geometric wrote:
The best way to tackle this question is probably the formula for three overlapping sets:

Total = Group1 + Group 2 + Group 3 - (sum of 2-group overlaps) - 2*(all three) + Neither

Total = 300(.4) + 300(.3) + 300(.75) - 300(.35) - 2*(all three) + 0
300*.1 = 30
300 = 120 + 90 + 225 - 105 - 2*(all three)
2*(all three) = 30
:. 15 experienced all three effects

So Group 1 + Group 2 + Group 3 - 2-group overlaps * 2 - 3-group overlaps * 3 is our answer
= 120 + 90 + 225 - 105*2 - 15*3
= 435 - 210 - 45
= 180


Why did you multiply 300 by 10% - where do you see such information that all three is 30 :? ....another confusion why here you use figures except of (all three) 300 = 120 + 90 + 225 - 105 - 2*(all three) if all three is unknown then we could use 3x = all three multiplied by 2 = 6x :?

and why are you using two equations ? where as Bunuel in his post provides one formula to apply when we have three groups ? https://gmatclub.com/forum/advanced-ove ... 44260.html which says: Total=A+B+C−(sum of EXACTLY 2−group overlaps)−2∗(all three)+Neither :)

Kudos [?]: 23 [0], given: 179

Manager
Manager
User avatar
B
Joined: 09 Mar 2016
Posts: 132

Kudos [?]: 23 [0], given: 179

Re: Of the 300 subjects who participated in an experiment using [#permalink]

Show Tags

New post 03 Jan 2018, 04:29
dave13 wrote:
geometric wrote:
The best way to tackle this question is probably the formula for three overlapping sets:

Total = Group1 + Group 2 + Group 3 - (sum of 2-group overlaps) - 2*(all three) + Neither

Total = 300(.4) + 300(.3) + 300(.75) - 300(.35) - 2*(all three) + 0
300*.1 = 30
300 = 120 + 90 + 225 - 105 - 2*(all three)
2*(all three) = 30
:. 15 experienced all three effects

So Group 1 + Group 2 + Group 3 - 2-group overlaps * 2 - 3-group overlaps * 3 is our answer
= 120 + 90 + 225 - 105*2 - 15*3
= 435 - 210 - 45
= 180


Why did you multiply 300 by 10% - where do you see such information that all three is 30 :? ....another confusion why here you use figures except of (all three) 300 = 120 + 90 + 225 - 105 - 2*(all three) if all three is unknown then we could use 3x = all three multiplied by 2 = 6x :?

and why are you using two equations ? where as Bunuel in his post provides one formula to apply when we have three groups ? https://gmatclub.com/forum/advanced-ove ... 44260.html which says: Total=A+B+C−(sum of EXACTLY 2−group overlaps)−2∗(all three)+Neither :)



these overlapping sets overlap both parts of my brain - totally confusing :-)

Kudos [?]: 23 [0], given: 179

Re: Of the 300 subjects who participated in an experiment using   [#permalink] 03 Jan 2018, 04:29

Go to page   Previous    1   2   3   [ 45 posts ] 

Display posts from previous: Sort by

Of the 300 subjects who participated in an experiment using

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.