Find all School-related info fast with the new School-Specific MBA Forum
Learn more about the recent changes... close

It is currently 18 May 2013, 10:20
Customize  |  Hide

Search
Register
New posts
Unanswered

How many numbers of 7 digits can be formed from the digits

  Question banks Downloads My Bookmarks Reviews  
  Oldest Best Reply
Search for:
 
Print view
First unread post
Author Message
TAGS:
Manager
Manager
Joined: 14 Mar 2007
Posts: 63
Followers: 1

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

GMAT Tests User
How many numbers of 7 digits can be formed from the digits [#permalink] New post 10 Aug 2007, 04:23
How many numbers of 7 digits can be formed from the digits 1,2,3,4,5,6,7 if there are not more than 2 digits between 1 and 2 ?

Please provide an explanation along with the solution. :-D
VP
VP
Joined: 10 Jun 2007
Posts: 1478
Followers: 5

Kudos [?]: 70 [0], given: 0

GMAT Tests User
Re: Nice P&C Question [#permalink] New post 10 Aug 2007, 07:45
ajay_gmat wrote:
How many numbers of 7 digits can be formed from the digits 1,2,3,4,5,6,7 if there are not more than 2 digits between 1 and 2 ?

Please provide an explanation along with the solution. :-D


Two digits between 1 and 2
1XX2XXX = 2*5!
X1XX2XX = 2*5!
XX1XX2X = 2*5!
XXX1XX2 = 2*5!

One digit between 1 and 2
1X2XXXX = 2*5!
X1X2XXX = 2*5!
XX1X2XX = 2*5!
XXX1X2X = 2*5!
XXXX1X2 = 2*5!

Total = 9*2*5! = 2160
Manager
Manager
Joined: 14 Mar 2007
Posts: 63
Followers: 1

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

GMAT Tests User
Re: Nice P&C Question [#permalink] New post 10 Aug 2007, 08:46
bkk145 wrote:
ajay_gmat wrote:
How many numbers of 7 digits can be formed from the digits 1,2,3,4,5,6,7 if there are not more than 2 digits between 1 and 2 ?

Please provide an explanation along with the solution. :-D


Two digits between 1 and 2
1XX2XXX = 2*5!
X1XX2XX = 2*5!
XX1XX2X = 2*5!
XXX1XX2 = 2*5!

One digit between 1 and 2
1X2XXXX = 2*5!
X1X2XXX = 2*5!
XX1X2XX = 2*5!
XXX1X2X = 2*5!
XXXX1X2 = 2*5!

Total = 9*2*5! = 2160


Thanks bkk145 for your reply. Could you explain why you are multiplying by 2 each time ? The Question says between 1 and 2 and i hence think that 1 and 2 are not interchangeable .. Any thoughts, am not sure myself ?
VP
VP
Joined: 10 Jun 2007
Posts: 1478
Followers: 5

Kudos [?]: 70 [0], given: 0

GMAT Tests User
Re: Nice P&C Question [#permalink] New post 10 Aug 2007, 09:01
ajay_gmat wrote:
bkk145 wrote:
ajay_gmat wrote:
How many numbers of 7 digits can be formed from the digits 1,2,3,4,5,6,7 if there are not more than 2 digits between 1 and 2 ?

Please provide an explanation along with the solution. :-D


Two digits between 1 and 2
1XX2XXX = 2*5!
X1XX2XX = 2*5!
XX1XX2X = 2*5!
XXX1XX2 = 2*5!

One digit between 1 and 2
1X2XXXX = 2*5!
X1X2XXX = 2*5!
XX1X2XX = 2*5!
XXX1X2X = 2*5!
XXXX1X2 = 2*5!

Total = 9*2*5! = 2160


Thanks bkk145 for your reply. Could you explain why you are multiplying by 2 each time ? The Question says between 1 and 2 and i hence think that 1 and 2 are not interchangeable .. Any thoughts, am not sure myself ?


Actually they are interchangeable. Digits between 1 and 2 means any number between those two, but it does not restrict that 1 and 2 cannot be interchangeable. You can have 1342 or 2341; hence you must multiple by 2 each time.
I hope the number I got was the right answer.
Re: Nice P&C Question   [#permalink] 10 Aug 2007, 09:01
    Similar topics Author Replies Last post
Similar
Topics:
 New posts How many numbers of 7 digits can be formed from the digits tsg 1 02 Feb 2004, 12:10
New posts How many numbers of 'n' digits can be formed from the sunniboy007 1 13 Mar 2004, 16:53
New posts How many 3 digit odd numbers can be formed from the set of rxs0005 7 13 Jan 2005, 06:22
New posts How many 5-digit numbers can be formed from the digits Ravshonbek 5 11 Nov 2007, 04:53
This topic is locked, you cannot edit posts or make further replies. New How many five digit numbers can be formed? WishMasterUA 1 04 Jun 2011, 04:17
Display posts from previous: Sort by

How many numbers of 7 digits can be formed from the digits

  Question banks Downloads My Bookmarks Reviews  
Print view
First unread post

Moderators: Bunuel, VeritasPrepKarishma

Search for:


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.

Main navigation

GMAT Resources

Partners

MBA Resources

www.gmac.com|www.mba.com