It is currently 22 Oct 2017, 23:29

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

In how many different ways (relative to each other) can 8

Author Message
TAGS:

Hide Tags

Manager
Status: struggling with GMAT
Joined: 06 Dec 2012
Posts: 203

Kudos [?]: 437 [0], given: 46

Concentration: Accounting
GMAT Date: 04-06-2013
GPA: 3.65
In how many different ways (relative to each other) can 8 [#permalink]

Show Tags

28 Feb 2013, 12:24
1
This post was
BOOKMARKED
00:00

Difficulty:

(N/A)

Question Stats:

50% (00:01) correct 50% (02:24) wrong based on 7 sessions

HideShow timer Statistics

In how many different ways (relative to each other) can 8 friends sit around a square table with 2 seats on each side of the table?

OA:
[Reveal] Spoiler:
2*7!

Kudos [?]: 437 [0], given: 46

Manager
Status: Helping People Ace the GMAT
Joined: 16 Jan 2013
Posts: 184

Kudos [?]: 54 [1], given: 4

Location: United States
Concentration: Finance, Entrepreneurship
GMAT 1: 770 Q50 V46
GPA: 3.1
WE: Consulting (Consulting)
Re: In how many different ways (relative to each other) can 8 [#permalink]

Show Tags

28 Feb 2013, 13:44
1
KUDOS
Normally the formula for items in a circle is (n-1)! - in this case this is the 7!

It is multiplied by 2 because of the rest of the information. If you have the same arrangement of people you can have everyone shift one position to the right (or left) and they will be sitting next to a different person. With 2 shifts they will be back to sitting next to the original person.

Hope this helps.
_________________

Want to Ace the GMAT with 1 button? Start Here:
GMAT Answers is an adaptive learning platform that will help you understand exactly what you need to do to get the score that you want.

Kudos [?]: 54 [1], given: 4

Current Student
Joined: 21 Aug 2014
Posts: 138

Kudos [?]: 225 [0], given: 49

GMAT 1: 610 Q49 V25
GMAT 2: 730 Q50 V40
Re: In how many different ways (relative to each other) can 8 [#permalink]

Show Tags

24 Jun 2015, 11:47
In how many different ways (relative to each other) can 8 friends sit around a square table with 2 seats on each side of the table?

A) 2 * 8!
B) 2 * 7!
C) $$\frac{8!}{4!}$$
D) (8-1)!
E) 8!/2

Kudos [?]: 225 [0], given: 49

Current Student
Joined: 21 Aug 2014
Posts: 138

Kudos [?]: 225 [0], given: 49

GMAT 1: 610 Q49 V25
GMAT 2: 730 Q50 V40
Re: In how many different ways (relative to each other) can 8 [#permalink]

Show Tags

24 Jun 2015, 11:49
[Reveal] Spoiler: option
D?

_________________

Please consider giving Kudos if you like my explanation

Kudos [?]: 225 [0], given: 49

Math Forum Moderator
Joined: 02 Aug 2009
Posts: 4994

Kudos [?]: 5525 [0], given: 112

Re: In how many different ways (relative to each other) can 8 [#permalink]

Show Tags

24 Jun 2015, 18:48
Patronus wrote:
In how many different ways (relative to each other) can 8 friends sit around a square table with 2 seats on each side of the table?

A) 2 * 8!
B) 2 * 7!
C) $$\frac{8!}{4!}$$
D) (8-1)!
E) 8!/2

Hi,
We can take this square as a circle but with one difference....
first, if it were a circle , the ways would be 7!..
now only difference is in each arrangement of 7!, any particular person would be sitting with two different person on an edge of the table
that is he would be sitting with the person on his left on one side of the square and with the one on his right in the next arrangement without shifting relatively to each other..
so we multiply each arrangement with 2.. ans 7!*2
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

Kudos [?]: 5525 [0], given: 112

Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7677

Kudos [?]: 17398 [0], given: 232

Location: Pune, India
Re: In how many different ways (relative to each other) can 8 [#permalink]

Show Tags

24 Jun 2015, 21:13
mun23 wrote:
In how many different ways (relative to each other) can 8 friends sit around a square table with 2 seats on each side of the table?
need the explanation..........I an not understanding how to solve

I gave the solution to this problem in the post after the post on circular arrangements:
http://www.veritasprep.com/blog/2011/10 ... ts-part-i/

It's explained in detail on the link given above.
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for \$199

Veritas Prep Reviews

Kudos [?]: 17398 [0], given: 232

Senior Manager
Status: Math is psycho-logical
Joined: 07 Apr 2014
Posts: 437

Kudos [?]: 139 [0], given: 169

Location: Netherlands
GMAT Date: 02-11-2015
WE: Psychology and Counseling (Other)
Re: In how many different ways (relative to each other) can 8 [#permalink]

Show Tags

25 Jun 2015, 04:08
I am not sure I understand this comopletely.

For me, all 8 seats for the first person are the same. But, if he sits on seat 1, then there are 7! remaining ways for the other people to be seated. If he seats on seat 2 (the other corner of that same side of the table) then there are 7! remaining ways for the rest of the people to be seated. The difference is that person one will be next to another person depending on which seat he chooses to sit on.

So, in this sense, 2*7! makes sense.

But, I don't get why 2-4-6-8 seats are the same and 1-3-5-7 similarly the same, creating the *2 in the response.

Kudos [?]: 139 [0], given: 169

Senior Manager
Status: Math is psycho-logical
Joined: 07 Apr 2014
Posts: 437

Kudos [?]: 139 [0], given: 169

Location: Netherlands
GMAT Date: 02-11-2015
WE: Psychology and Counseling (Other)
Re: In how many different ways (relative to each other) can 8 [#permalink]

Show Tags

25 Jun 2015, 04:18
pacifist85 wrote:
I am not sure I understand this comopletely.

For me, all 8 seats for the first person are the same. But, if he sits on seat 1, then there are 7! remaining ways for the other people to be seated. If he seats on seat 2 (the other corner of that same side of the table) then there are 7! remaining ways for the rest of the people to be seated. The difference is that person one will be next to another person depending on which seat he chooses to sit on.

So, in this sense, 2*7! makes sense.

But, I don't get why 2-4-6-8 seats are the same and 1-3-5-7 similarly the same, creating the *2 in the response.

OK... I just realised that the first person choosing seat 1 or 2 , and generally choosing 1-3-5-7 or 2-4-6-8 is actually exactly the same thing...

Kudos [?]: 139 [0], given: 169

Re: In how many different ways (relative to each other) can 8   [#permalink] 25 Jun 2015, 04:18
Display posts from previous: Sort by