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

It is currently 12 Jul 2014, 19:00

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

Combinations

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Current Student
avatar
Joined: 21 Oct 2009
Posts: 41
Followers: 0

Kudos [?]: 4 [0], given: 4

Combinations [#permalink] New post 27 Oct 2009, 22:29
This question doesn't come from GMAT text book. It just popped up in my mind during my study.
Given a set of letters (A,B,C), how many combinations of 4 letters are there, using both A and C at least once? You don't have to use all of them. Besides, (AACC), (CCAA),(ACAC),(CACA),(CAAC) and (ACCA) are all considered same.

I am kind of comfused during the caliculation. pLease help me.
Kaplan GMAT Prep Discount CodesKnewton GMAT Discount CodesManhattan GMAT Discount Codes
Expert Post
2 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 18514
Followers: 3193

Kudos [?]: 21353 [2] , given: 2546

Re: Combinations [#permalink] New post 27 Oct 2009, 23:54
2
This post received
KUDOS
Expert's post
yuskay wrote:
This question doesn't come from GMAT text book. It just popped up in my mind during my study.
Given a set of letters (A,B,C), how many combinations of 4 letters are there, using both A and C at least once? You don't have to use all of them. Besides, (AACC), (CCAA),(ACAC),(CACA),(CAAC) and (ACCA) are all considered same.

I am kind of comfused during the caliculation. pLease help me.


Let me put it this way if I got it right:

We have 3 letters A,B and C. We want to form 4 letter combination from this letters, with condition that:
1. Order doesn't matter.
2. We should use at least once A and C, but not necessarily B.
How many such combinations are possible?

If it's so then, let's fix TWO letters AC, as they always should present.

We can easily right down all the possibilities.
Fixed AC as we must use them and any 3 left letter from the set:
ACAA
ACAB
ACAC
ACBB
ACBC
ACCC
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Current Student
avatar
Joined: 21 Oct 2009
Posts: 41
Followers: 0

Kudos [?]: 4 [0], given: 4

Re: Combinations [#permalink] New post 28 Oct 2009, 01:47
Bunuel, thank you!
Re: Combinations   [#permalink] 28 Oct 2009, 01:47
    Similar topics Author Replies Last post
Similar
Topics:
Experts publish their posts in the topic Combinations mads 4 21 Mar 2010, 21:03
Combinations axl_oz 6 05 Feb 2009, 17:48
1 COMBINATIONS vcbabu 9 02 Feb 2009, 10:36
combinations joemama142000 5 25 Apr 2006, 09:29
Combinations sair 13 08 Sep 2004, 09:40
Display posts from previous: Sort by

Combinations

  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®.