m01 q24 : GMAT Club Tests

m01 q24

Oldest

Best Reply

Author

Message

Manager

Joined: 05 Jun 2009

Posts: 77

Followers: 1

Kudos [?]: 2 [0], given: 1

m01 q24 [#permalink]

24 Dec 2009, 14:24

If 5 noble knights are to be seated at a round table, then how many different ways can they be seated?

120
96
60
35
24

Can someone explain this to me?

Thanks so much

Senior Manager

Joined: 30 Aug 2009

Posts: 296

Location: India

Concentration: General Management

Followers: 2

Kudos [?]: 65 [0], given: 5

Re: m01 q24 [#permalink]

26 Dec 2009, 12:00

sfeiner wrote:

If 5 noble knights are to be seated at a round table, then how many different ways can they be seated?

120
96
60
35
24

Can someone explain this to me?

Thanks so much

for a round table if we have n people then number of arrangements will be (n-1)!.
Its same as we fix one of the people and then (n-1) people can be seated in (n-1)! ways

so for 5 people we will have (5-1)!= 4! = 24

Ans E

Intern

Joined: 07 Oct 2009

Posts: 33

Followers: 0

Kudos [?]: 3 [0], given: 1

Re: m01 q24 [#permalink]

26 Dec 2009, 12:34

Just remember the formula-

N things/people can be arranged in straight line in N! ways

N things/people can be arranged in circular line in (N-1)! ways

Manager

Joined: 05 Jun 2009

Posts: 77

Followers: 1

Kudos [?]: 2 [0], given: 1

Re: m01 q24 [#permalink]

26 Dec 2009, 13:34

I assumed it would be N! but because its a circular table its (N-1)!? so 24?

So if the question had said 5 spots in a line it would be N! so 120 instead?

Sorry but I really didn't understand this

Thanks,

SF

Intern

Joined: 07 Oct 2009

Posts: 33

Followers: 0

Kudos [?]: 3 [1] , given: 1

Re: m01 q24 [#permalink]

27 Dec 2009, 08:34

This post received
KUDOS

Yes SF, had it been a straight line, the answer is N!,i.e.,120..just because question says it to be a circular table, answer is (N-1)!,i.e, 24.

I hope below explanation helps

Case1: Straight table.

5 people can sit like this, the first seat can be occupied by 5 knights, to occupy next seat there are only 4 knights, for third seat there are only 3 & so on.Multiply them all as it is 'AND' case.

5*4*3*2*1= 5!=120

Case 2: Circular table

It is difficult point out which is the first seat in a circular table.So we assume any one seat to be a first seat and one knight sits there. Now we have 4 seats and 4 knights to be arranged.Applying same logic as above.

i.e, second seat can be occupied by any 4 remaining knights,next seat by any 3 and so on.

4*3*2*1=4!=24

I hope now it's clear.

Manager

Joined: 05 Jun 2009

Posts: 77

Followers: 1

Kudos [?]: 2 [0], given: 1

Re: m01 q24 [#permalink]

27 Dec 2009, 14:03

Thanks!

That was really very clear, kudos.

SF

Intern

Joined: 04 Jan 2010

Posts: 5

Followers: 0

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

Re: m01 q24 [#permalink]

04 Jan 2010, 02:33

Well, great work! You have helped me to improve my knowledge about this field. Thank you so much for sharing.

Re: m01 q24 [#permalink] 04 Jan 2010, 02:33

		Similar topics	Author	Replies	Last post
Similar Topics:		m01-q24	pmal04	9	16 May 2009, 07:39
		M01 Q24	ThrillRide	2	07 Jul 2009, 07:26
		M01Q24	DenisSh	1	07 Sep 2009, 00:27
	2	M01, Q24	sunman	2	29 Dec 2011, 15:55

m01 q24

Moderator: Bunuel

Main navigation

GMAT Resources

Partners

MBA Resources

GMAT ® is a registered trademark of the Graduate Management Admission Council ® (GMAC ®). GMAT Club's website has not been reviewed or endorsed by GMAC.

GMAT Courses

Admissions Consulting

m01 q24

m01 q24

Main navigation

GMAT Resources

Partners

MBA Resources