Two members of a certain club are selected to speak at the next club : GMAT Problem Solving (PS)
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 18 Jan 2017, 15:55

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Two members of a certain club are selected to speak at the next club

Author Message
TAGS:

### Hide Tags

VP
Joined: 30 Jun 2008
Posts: 1043
Followers: 14

Kudos [?]: 567 [0], given: 1

Two members of a certain club are selected to speak at the next club [#permalink]

### Show Tags

20 Sep 2008, 22:13
2
This post was
BOOKMARKED
00:00

Difficulty:

5% (low)

Question Stats:

87% (02:04) correct 13% (01:45) wrong based on 130 sessions

### HideShow timer Statistics

Two members of a certain club are selected to speak at the next club meeting. If there are 36 different possible selections of the 2 club members, how many members does the club have?

A. 5
B. 6
C. 7
D. 8
E. 9
[Reveal] Spoiler: OA

_________________

"You have to find it. No one else can find it for you." - Bjorn Borg

Last edited by Bunuel on 22 Nov 2014, 06:07, edited 1 time in total.
Renamed the topic, edited the question, added the OA and moved to PS forum.
VP
Joined: 30 Jun 2008
Posts: 1043
Followers: 14

Kudos [?]: 567 [0], given: 1

Re: Two members of a certain club are selected to speak at the next club [#permalink]

### Show Tags

20 Sep 2008, 23:46
1
This post was
BOOKMARKED
I did it this way.

we know total number of ways of selecting 2 People out of n people is nC2 = 36(given in the question)

ie n!/(2!*(n-2)!) = [n(n-1)*(n-2)!] / [(2!*(n-2)!)] = n(n-1)/2

so n(n-1)/2=36
n(n-1)=72
we know 72 = 9*8

so n=9

is the approach right ?
_________________

"You have to find it. No one else can find it for you." - Bjorn Borg

SVP
Joined: 17 Jun 2008
Posts: 1569
Followers: 11

Kudos [?]: 250 [0], given: 0

Re: Two members of a certain club are selected to speak at the next club [#permalink]

### Show Tags

22 Sep 2008, 00:52
amitdgr wrote:
I did it this way.

we know total number of ways of selecting 2 People out of n people is nC2 = 36(given in the question)

ie n!/(2!*(n-2)!) = [n(n-1)*(n-2)!] / [(2!*(n-2)!)] = n(n-1)/2

so n(n-1)/2=36
n(n-1)=72
we know 72 = 9*8

so n=9

is the approach right ?

I used exactly the same approach.
Current Student
Joined: 04 Jul 2014
Posts: 285
Location: India
GMAT 1: 640 Q47 V31
GMAT 2: 640 Q44 V34
GMAT 3: 710 Q49 V37
GPA: 3.58
WE: Analyst (Accounting)
Followers: 19

Kudos [?]: 230 [0], given: 403

Re: Two members of a certain club are selected to speak at the next club [#permalink]

### Show Tags

22 Nov 2014, 02:54
I used the same approach too. Don't see another way. Do you have an OA/OE?
_________________

Cheers!!

JA
If you like my post, let me know. Give me a kudos!

Math Expert
Joined: 02 Sep 2009
Posts: 36548
Followers: 7077

Kudos [?]: 93109 [1] , given: 10552

Re: Two members of a certain club are selected to speak at the next club [#permalink]

### Show Tags

22 Nov 2014, 06:10
1
KUDOS
Expert's post
joseph0alexander wrote:
I used the same approach too. Don't see another way. Do you have an OA/OE?

Solution above is correct. Similar question to practice: two-members-of-a-club-are-to-be-selected-to-represent-the-132340.html
_________________
Intern
Joined: 12 Apr 2015
Posts: 6
Followers: 0

Kudos [?]: 0 [0], given: 88

Re: Two members of a certain club are selected to speak at the next club [#permalink]

### Show Tags

21 Jul 2015, 09:02
This one was easiest for me to solve by backsolving. I didn't bother with Algebra: Too much potential for mistakes.

Test answer B: 6C2 = 15. We need a number bigger than 6 to get us to 36. Eliminate A & B.
Test answer D: 8C2 = 28. Still not big enough. The answer must be E.

Only had to use 2 calculations. Proof: 9C2 = 36.

This is a great example of a problem that can be solved fastest by using the answers.
VP
Joined: 08 Jul 2010
Posts: 1443
Location: India
GMAT: INSIGHT
WE: Education (Education)
Followers: 68

Kudos [?]: 1407 [0], given: 42

Re: Two members of a certain club are selected to speak at the next club [#permalink]

### Show Tags

21 Jul 2015, 09:35
amitdgr wrote:
Two members of a certain club are selected to speak at the next club meeting. If there are 36 different possible selections of the 2 club members, how many members does the club have?

A. 5
B. 6
C. 7
D. 8
E. 9

Method-1

Total No. of Selection of r out of n objects are defined by nCr = n! / [(r!)(n-r)!]

i.e. If total member = n
then nC2 = n! / [(2!)(n-2)!] = 36

i.e. n*(n-1)*(n-2)! / [(2!)(n-2)!] = 36
i.e. n*(n-1) = 72

but 9*8 = 72 (for Positive Values of n)
therefore, n*(n-1) = 9*8
i.e. n= 9

Method-2
Let, Total members = n
@n=2, no. of ways to select 2 out of 2(A,B) = (AB) = 1
@n=3, no. of ways to select 2 out of 3(A,B,C) = (AB, AC, BC) = 2+1 = 3
@n=4, no. of ways to select 2 out of 4(A,B,C,D) = (AB, AC, AD, BC, BD, CD) = 3+2+1 = 6

i.e. @n=5, Total Selection of 2 = 4+3+2+1 = 10
i.e. @n=6, Total Selection of 2 = 5+4+3+2+1 = 15
i.e. @n=7, Total Selection of 2 = 6+5+4+3+2+1 = 21
i.e. @n=8, Total Selection of 2 = 7+6+5+4+3+2+1 = 28
i.e. @n=9, Total Selection of 2 = 8+7+6+5+4+3+2+1 = 36

_________________

Prosper!!!
GMATinsight
Bhoopendra Singh and Dr.Sushma Jha
e-mail: info@GMATinsight.com
Call us : +91-9999687183 / 9891333772
http://www.GMATinsight.com/testimonials.html

Feel free to give a Kudos if it is a useful post .

Re: Two members of a certain club are selected to speak at the next club   [#permalink] 21 Jul 2015, 09:35
Similar topics Replies Last post
Similar
Topics:
25 Last year 26 members of a certain club traveled to England, 26 members 13 15 Jun 2016, 00:35
3 In a certain book club, the members are voting between two books – a 4 24 Mar 2016, 01:49
3 Two members of a club are to be selected to represent the 3 10 May 2012, 07:15
2 At a certain health club, 30% of the members use both pool a 6 07 Mar 2010, 09:25
17 A certain club has 20 members. What is the ratio of the memb 20 25 Mar 2009, 22:04
Display posts from previous: Sort by