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ddm: Master | Next Rank: 500 Posts; Posts: 162; Joined: Mon Jul 28, 2008 8:33 pm; Location: San Jose,CA; Thanked: 1 times

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by ddm » Mon Aug 25, 2008 2:52 pm

Each of the 59 members in a high school class is required to sign up for a minimum of one and a maximum of three academic clubs. The three clubs to choose from are the poetry club, the history club, and the writing club. A total of 22 students sign up for the poetry club, 27 students for the history club, and 28 students for the writing club. If 6 students sign up for exactly two clubs, how many students sign up for all three clubs?

2
5
6
8
9

OA-C

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Source: Beat The GMAT — Problem Solving | Mon Aug 25, 2008 2:52 pm

just_do_it: Senior | Next Rank: 100 Posts; Posts: 73; Joined: Thu Aug 07, 2008 7:33 pm; Thanked: 7 times; Followed by:1 members

by just_do_it » Mon Aug 25, 2008 3:50 pm

this problem is easier to solve using venn diagram. Please refer to the attached image.

from the given information

D+A+X+C = P = 22
F+A+X+B = H =27
E+B+X+C = W = 28
(D+F+E) + (A+B+C) + X = 59
A+B+C=6

adding first 3 equations,
(D+E+F)+2(A+B+C)+3X=77
Subtracting the above equation from the 4th equation
(A+B+C)+2X=18
6+2X=18
or X=6 (option c)

Hope this helps.

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pre-gmat: Master | Next Rank: 500 Posts; Posts: 105; Joined: Tue Jul 15, 2008 7:03 pm; Thanked: 5 times

by pre-gmat » Mon Aug 25, 2008 3:51 pm

I am not sure of the Venn Diagram...if someone knows that route...it'll be a good idea to explain...here's what I think and I remember seeing this on one of the forums:

there are total 59 students but according to the question
(22+27+28) signed up which is 18 extra counts. The question states 6 signed up exactly for 2 clubs. we are left with 12 and now out of these the people who have signed in all the 3 clubs count for 2 extra sign ups which is 6 so subtract 6 from 12 and you get 6 who signed up for all three clubs.

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kuroneko1313: Senior | Next Rank: 100 Posts; Posts: 35; Joined: Thu Aug 21, 2008 2:55 pm; Thanked: 1 times

by kuroneko1313 » Mon Aug 25, 2008 4:10 pm

just_do_it, your Venn Diagram is not showing. Could you probably re-attach it?

pre-gmat, I was following your explanation but got lost on this bolded part, can you please clearify?

pre-gmat wrote:we are left with 12 and now out of these the people who have signed in all the 3 clubs count for 2 extra sign ups which is 6 so subtract 6 from 12 and you get 6 who signed up for all three clubs.

Thanks!