Check GMAT Club Decision Tracker for the Latest School Decision Releases https://gmatclub.com/AppTrack

 It is currently 23 May 2017, 16:59

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

Everyone shakes hands with everyone else in a room. Total number of ha

Author Message
TAGS:

Hide Tags

Senior Manager
Joined: 13 Aug 2010
Posts: 299
Followers: 1

Kudos [?]: 25 [0], given: 1

Everyone shakes hands with everyone else in a room. Total number of ha [#permalink]

Show Tags

12 Oct 2010, 21:27
00:00

Difficulty:

(N/A)

Question Stats:

100% (01:03) correct 0% (00:00) wrong based on 8 sessions

HideShow timer Statistics

Everyone shakes hands with everyone else in a room. Total number of handshakes is 66. Number of persons=?

a. 14
b. 12
c. 11
d. 15
e. 16
[Reveal] Spoiler: OA
Retired Moderator
Joined: 02 Sep 2010
Posts: 803
Location: London
Followers: 110

Kudos [?]: 1020 [0], given: 25

Re: Everyone shakes hands with everyone else in a room. Total number of ha [#permalink]

Show Tags

12 Oct 2010, 22:06
prab wrote:
Everyone shakes hands with everyone else in a room. Total number of handshakes is 66. Number of persons=?

a.14
b.12
c.11
d.15
e.16

In a room of n people, the number of possible handshakes is C(n,2) or n(n-1)/2

So n(n-1)/2 = 66 OR n(n-1)=132 OR n=12

_________________
Senior Manager
Joined: 13 Aug 2010
Posts: 299
Followers: 1

Kudos [?]: 25 [0], given: 1

Re: Everyone shakes hands with everyone else in a room. Total number of ha [#permalink]

Show Tags

12 Oct 2010, 22:19
can you please explain why are we using n(n-1)/2, m not able to grab the concept.
Retired Moderator
Joined: 02 Sep 2010
Posts: 803
Location: London
Followers: 110

Kudos [?]: 1020 [0], given: 25

Re: Everyone shakes hands with everyone else in a room. Total number of ha [#permalink]

Show Tags

12 Oct 2010, 22:34
Number of handshakes will be the number of ways to choose 2 people out of n people. For every choice of two people, there is a handshake.

This number is C(n,2) = $$\frac{n!}{(n-2)!2!}$$
_________________
Re: Everyone shakes hands with everyone else in a room. Total number of ha   [#permalink] 12 Oct 2010, 22:34
Similar topics Replies Last post
Similar
Topics:
1 Jason has a handful of dimes and quarters. There are a total of 22 coi 1 11 Apr 2017, 18:27
3 6 people meet for a business lunch. Each person shakes hands once with 3 12 May 2016, 21:16
7 If 11 persons meet at a reunion and each person shakes hands exactly o 8 23 Mar 2016, 08:00
7 If 10 persons meet at a reunion and each person shakes hands 5 29 Mar 2017, 10:00
8 There are 10 people in a room. If each person shakes hands with exactl 12 24 Apr 2017, 05:12
Display posts from previous: Sort by