Find all School-related info fast with the new School-Specific MBA Forum

It is currently 02 Sep 2015, 20:31
GMAT Club Tests

Close

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
Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

How many different ways to pick 3 letters from ABCDEFG, when

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Senior Manager
Senior Manager
User avatar
Joined: 01 May 2004
Posts: 337
Location: USA
Followers: 1

Kudos [?]: 29 [0], given: 0

How many different ways to pick 3 letters from ABCDEFG, when [#permalink] New post 27 Nov 2004, 16:59
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

How many different ways to pick 3 letters from ABCDEFG, when AB can't be together?
Manager
Manager
avatar
Joined: 30 Jul 2004
Posts: 101
Followers: 1

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

 [#permalink] New post 27 Nov 2004, 20:57
To choose 3 letters out of ABCDEFG without AB together :
we have to consider AB as ONE letter

so we have to choose 3 letters out of 6(since AB are one letter)

No. of ways to choosing are c(6,3) = 20.

What is the answer ?
Manager
Manager
avatar
Joined: 13 Oct 2004
Posts: 236
Followers: 1

Kudos [?]: 9 [0], given: 0

 [#permalink] New post 28 Nov 2004, 09:47
There are 3 ways in which AB cant be together.

A Not B or B not A or Neither A Nor B
A Not B = 3(1. 5.4) = 60
B Not A = 3(1.5.4) = 60
Neither A Nor B = 5.4.3 = 60

180, if order matters.

If order doesnt matter: 5c2+5c2+5c3 = 30.

Last edited by prep_gmat on 28 Nov 2004, 17:25, edited 1 time in total.
Director
Director
User avatar
Joined: 31 Aug 2004
Posts: 610
Followers: 3

Kudos [?]: 59 [0], given: 0

 [#permalink] New post 28 Nov 2004, 14:06
Various ways : 7C3

AB together : 5!

So 7C3-5!
Manager
Manager
avatar
Joined: 13 Oct 2004
Posts: 236
Followers: 1

Kudos [?]: 9 [0], given: 0

 [#permalink] New post 28 Nov 2004, 17:27
Twixt,
7c3 - 5! would yield a negative number?.
Director
Director
User avatar
Joined: 16 Jun 2004
Posts: 893
Followers: 2

Kudos [?]: 29 [0], given: 0

 [#permalink] New post 28 Nov 2004, 19:16
oops late on this one..

2C1*5C2 + 5C3 = 30.

2C1 because - either of A or B.
5C2 2 of the remaining 5 letters

5C3 - pick all three letters from the 5.
Director
Director
User avatar
Joined: 31 Aug 2004
Posts: 610
Followers: 3

Kudos [?]: 59 [0], given: 0

 [#permalink] New post 29 Nov 2004, 02:57
I am sorry my answer was 7C3 - 5 and not 7C3 - 5! (5! makes no sense since there is only one slot left with 5 letters to put into...)

=5.6.7/6-5=35-5=30
Director
Director
User avatar
Joined: 07 Nov 2004
Posts: 690
Followers: 5

Kudos [?]: 35 [0], given: 0

 [#permalink] New post 29 Nov 2004, 04:45
In a question like this do we assume that the order of the letters do not matter? :?
Manager
Manager
User avatar
Joined: 31 Aug 2004
Posts: 166
Location: Vancouver, BC, Canada
Followers: 1

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

 [#permalink] New post 29 Nov 2004, 10:15
To Twist & Vprabhala,

Your answer is 7C3-5. How do you figure out that "5"?
Write out all the possibilities like the attached file?
Is there any better way to find this number?

:stupid
Attachments

letters.doc [19 KiB]
Downloaded 63 times

To download please login or register as a user

Director
Director
User avatar
Joined: 31 Aug 2004
Posts: 610
Followers: 3

Kudos [?]: 59 [0], given: 0

 [#permalink] New post 29 Nov 2004, 12:38
As order does not matter, you have to consider a 3 slots box. A is in 1st slot, B in the 2nd one, then you can put any of the 5 remaining letters in the last one.
Director
Director
User avatar
Joined: 07 Nov 2004
Posts: 690
Followers: 5

Kudos [?]: 35 [0], given: 0

 [#permalink] New post 29 Nov 2004, 15:38
twixt wrote:
As order does not matter, you have to consider a 3 slots box. A is in 1st slot, B in the 2nd one, then you can put any of the 5 remaining letters in the last one.


Why is it assumed that order does not matter? :stupid
Director
Director
User avatar
Joined: 21 Sep 2004
Posts: 612
Followers: 1

Kudos [?]: 11 [0], given: 0

 [#permalink] New post 30 Nov 2004, 09:31
as it is not mentioned.. we choose the lesser evil :roll:
  [#permalink] 30 Nov 2004, 09:31
Display posts from previous: Sort by

How many different ways to pick 3 letters from ABCDEFG, when

  Question banks Downloads My Bookmarks Reviews Important topics  


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®.