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

It is currently 25 May 2013, 12:06
Customize  |  Hide

Search
Register
New posts
Unanswered

In how many different ways can trhee letters be posted from

  Question banks Downloads My Bookmarks Reviews  
  Oldest Best Reply
Search for:
 
Print view
First unread post
Author Message
TAGS:
VP
VP
User avatar
Joined: 09 Jul 2007
Posts: 1114
Location: London
Followers: 4

Kudos [?]: 55 [0], given: 0

GMAT Tests User
In how many different ways can trhee letters be posted from [#permalink] New post 10 Nov 2007, 13:00
00:00

Question Stats:

33% (01:42) correct 66% (01:56) wrong based on 0 sessions
1. In how many different ways can trhee letters be posted from seven different postboxes assuming no two letters can be posted from the same postbox?

2. what if there is no restriction, that is, if two or more letters can be posted from the same box?

warm up :)
GMAT Club team member
User avatar
Joined: 02 Sep 2009
Posts: 11634
Followers: 1802

Kudos [?]: 9611 [0], given: 829

GMAT Tests User CAT Tests
Top Member of the Month
Re: counting principles [#permalink] New post 18 Nov 2009, 05:55
1. In how many different ways can trhee letters be posted from seven different postboxes assuming no two letters can be posted from the same postbox?

First letter could be sent from ANY of the seven postboxes - 7 (7 options);
Second letter could be sent from the SIX postboxes left - 6 (6 options);
Third letter could be sent from the FIVE postboxes left - 5 (5 options);

Total # of ways =7*6*5=210

2. what if there is no restriction, that is, if two or more letters can be posted from the same box?

In this problem we don't have restriction, thus ANY letter could be sent from ANY postboxes =7*7*7=7^3=343
_________________

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

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. NEW!!!

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. NEW!!!


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

Find out what's new at GMAT Club - latest features and updates

Senior Manager
Senior Manager
User avatar
Joined: 22 Dec 2009
Posts: 368
Followers: 9

Kudos [?]: 137 [0], given: 47

GMAT ToolKit User GMAT Tests User
Re: counting principles [#permalink] New post 17 Feb 2010, 03:47
Ravshonbek wrote:
1. In how many different ways can trhee letters be posted from seven different postboxes assuming no two letters can be posted from the same postbox?

2. what if there is no restriction, that is, if two or more letters can be posted from the same box?

warm up :)


1. 7 x 6 x 5 = 210
2. 7 x 7 x 7 = 343
_________________

Cheers!
JT...........
If u like my post..... payback in Kudos!! :beer

|Do not post questions with OA|Please underline your SC questions while posting|Try posting the explanation along with your answer choice|
|For CR refer Powerscore CR Bible|For SC refer Manhattan SC Guide|


~~Better Burn Out... Than Fade Away~~

Verbal GMAT Forum Moderator
Verbal GMAT Forum Moderator
Joined: 23 Oct 2011
Posts: 280
Followers: 13

Kudos [?]: 154 [0], given: 19

GMAT Tests User
Re: counting principles [#permalink] New post 10 Feb 2012, 04:03
Bunuel wrote:
1. In how many different ways can trhee letters be posted from seven different postboxes assuming no two letters can be posted from the same postbox?

First letter could be sent from ANY of the seven postboxes - 7 (7 options);
Second letter could be sent from the SIX postboxes left - 6 (6 options);
Third letter could be sent from the FIVE postboxes left - 5 (5 options);

Total # of ways =7*6*5=210

2. what if there is no restriction, that is, if two or more letters can be posted from the same box?

In this problem we don't have restriction, thus ANY letter could be sent from ANY postboxes =7*7*7=7^3=343


Hi Bunuel,

Could you please elaborate on the second question. Couldn't figure out why.
_________________

********************
Push +1 kudos button please, if you like my post.

Manager
Manager
Joined: 10 Jan 2010
Posts: 194
Location: Germany
Concentration: Strategy, General Management
Schools: IE '15 (M)
GMAT 1: Q V
GPA: 3
WE: Consulting (Telecommunications)
Followers: 2

Kudos [?]: 15 [0], given: 7

GMAT Tests User
Re: In how many different ways can trhee letters be posted from [#permalink] New post 10 Feb 2012, 05:05
1. 7 (no restriction) * 6 (can not be the same as the first one) * 5 (can not be the same as the first and second one) = 210
2. 7 (no restriction) * 7 (no restriction) * 7 (no restriction) = 343
1 KUDOS received
GMAT Club team member
User avatar
Joined: 02 Sep 2009
Posts: 11634
Followers: 1802

Kudos [?]: 9611 [1] , given: 829

GMAT Tests User CAT Tests
Top Member of the Month
Re: counting principles [#permalink] New post 10 Feb 2012, 09:13
1
This post received
KUDOS
mohankumarbd wrote:
Bunuel wrote:
1. In how many different ways can trhee letters be posted from seven different postboxes assuming no two letters can be posted from the same postbox?

First letter could be sent from ANY of the seven postboxes - 7 (7 options);
Second letter could be sent from the SIX postboxes left - 6 (6 options);
Third letter could be sent from the FIVE postboxes left - 5 (5 options);

Total # of ways =7*6*5=210

2. what if there is no restriction, that is, if two or more letters can be posted from the same box?

In this problem we don't have restriction, thus ANY letter could be sent from ANY postboxes =7*7*7=7^3=343


Hi Bunuel,

Could you please elaborate on the second question. Couldn't figure out why.


Welcome to GMAT Club. Please find below answer to your question:

"Two or more letters can be posted from the same box" means that all 3 letters can be posted from the same postbox (so we don't have the restriction we had for the first question).

Now, since there are 7 postboxes then each of these 3 letters has 7 options to be posted from, total # of ways is 7*7*7=7^3.

Hope it's clear.
_________________

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

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. NEW!!!

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. NEW!!!


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

Find out what's new at GMAT Club - latest features and updates

Intern
Intern
Joined: 14 Nov 2011
Posts: 24
Location: United States
Concentration: General Management, Entrepreneurship
Schools: Stanford '15
GPA: 3.61
WE: Consulting (Manufacturing)
Followers: 0

Kudos [?]: 5 [0], given: 13

Re: counting principles [#permalink] New post 25 May 2013, 08:22
Bunuel wrote:
mohankumarbd wrote:
Bunuel wrote:
1. In how many different ways can trhee letters be posted from seven different postboxes assuming no two letters can be posted from the same postbox?

First letter could be sent from ANY of the seven postboxes - 7 (7 options);
Second letter could be sent from the SIX postboxes left - 6 (6 options);
Third letter could be sent from the FIVE postboxes left - 5 (5 options);

Total # of ways =7*6*5=210

2. what if there is no restriction, that is, if two or more letters can be posted from the same box?

In this problem we don't have restriction, thus ANY letter could be sent from ANY postboxes =7*7*7=7^3=343


Hi Bunuel,

Could you please elaborate on the second question. Couldn't figure out why.


Welcome to GMAT Club. Please find below answer to your question:

"Two or more letters can be posted from the same box" means that all 3 letters can be posted from the same postbox (so we don't have the restriction we had for the first question).

Now, since there are 7 postboxes then each of these 3 letters has 7 options to be posted from, total # of ways is 7*7*7=7^3.

Hope it's clear.



Hi Bunnel,

I tried to do the second question via combinatorics, but i am not able to figure it out, please check the below method and guide where i went wrong

= all three in one box +2 in one box and the last one in a different box + all three in different boxes
= 3c3*7+3c2*7c1*6c5+3c1*7c3
= 7+ 3*7*6+3*7*6*5
= 7 + 126 + 270 = wrong
Re: counting principles   [#permalink] 25 May 2013, 08:22
    Similar topics Author Replies Last post
Similar
Topics:
 New posts Given letters ABCCD how many different ways can a group of Praetorian 3 18 Sep 2003, 12:53
Popular new posts In how many ways can one post 5 letters in 10 different sunniboy007 10 25 Jan 2004, 17:08
Popular new posts How many ways can we select three letters from the letters TeHCM 14 15 Nov 2005, 19:35
New posts In how many different ways can the letters in the word rlevochkin 5 19 Jan 2006, 11:54
New posts 1 In how many different ways can the letters of the world xALIx 2 17 Jun 2008, 10:05
Display posts from previous: Sort by

In how many different ways can trhee letters be posted from

  Question banks Downloads My Bookmarks Reviews  
Print view
First unread post

Moderators: Bunuel, VeritasPrepKarishma, IanStewart

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