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

It is currently 29 Aug 2014, 00:03

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

Symmetric Problem...Akamai..Please explain

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
CEO
CEO
avatar
Joined: 15 Aug 2003
Posts: 3470
Followers: 60

Kudos [?]: 665 [0], given: 781

Symmetric Problem...Akamai..Please explain [#permalink] New post 24 Aug 2003, 13:36
Hello akamai

i am referring to the following problem.
How many three digit numbers are there so that they can have 2 equal digits and the other digit different from these two?
paraphrasing your explanation..
10 pairs of numbers combine with 9 other numbers...total numbers ...
10*9 = 90
next there are three different ways in which the number can be arranged...AAB, ABA, BAA...so the total is 270

Next, we have to remove numbers that start with 0.
here you mention, since this is a "symmetric problem", exactly 1/10 of the numbers start with 0. so the final answer is 270 *0.9 =243


I need some help with the "symmetric " part ....can u please explain in brief.

Thanks
Praetorian







[/b]
GMAT Instructor
User avatar
Joined: 07 Jul 2003
Posts: 771
Location: New York NY 10024
Schools: Haas, MFE; Anderson, MBA; USC, MSEE
Followers: 9

Kudos [?]: 26 [0], given: 0

GMAT Tests User
Re: Symmetric Problem...Akamai..Please explain [#permalink] New post 24 Aug 2003, 15:42
praetorian123 wrote:
Hello akamai

i am referring to the following problem.
How many three digit numbers are there so that they can have 2 equal digits and the other digit different from these two?
paraphrasing your explanation..
10 pairs of numbers combine with 9 other numbers...total numbers ...
10*9 = 90
next there are three different ways in which the number can be arranged...AAB, ABA, BAA...so the total is 270

Next, we have to remove numbers that start with 0.
here you mention, since this is a "symmetric problem", exactly 1/10 of the numbers start with 0. so the final answer is 270 *0.9 =243


I need some help with the "symmetric " part ....can u please explain in brief.

Thanks
Praetorian







[/b]


The symmetric part means every number is equally likely to be in the first digit spot. Since there are 10 numbers, the likelyhood of a zero being in the first spot is simply 1/10.
_________________

Best,

AkamaiBrah
Former Senior Instructor, Manhattan GMAT and VeritasPrep
Vice President, Midtown NYC Investment Bank, Structured Finance IT
MFE, Haas School of Business, UC Berkeley, Class of 2005
MBA, Anderson School of Management, UCLA, Class of 1993

Manager
Manager
avatar
Joined: 10 Jun 2003
Posts: 213
Location: Maryland
Followers: 2

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

GMAT Tests User
 [#permalink] New post 25 Aug 2003, 06:11
In this problem, each number 100 - 999 can fall into one of three categories.

(1) All three digits are the same
(2) All three digits are different
(3) Two digits are the same and one is different

One method is to calculate the total # of numbers, and subtract (1) and (2) to leave (3)

Total # of numbers is 900 (999 - 100 + 1)

(1) there are 9 (111, 222, etc...)
(2) 9 possibilities for the first (can't be zero), 9 possibilities for the second (can't be the first), 8 possibilities for the last (can't be either of the first two). 9*9*8 = 648

900 - 9 - 648 = 243
_________________

Sept 3rd

  [#permalink] 25 Aug 2003, 06:11
    Similar topics Author Replies Last post
Similar
Topics:
11 Experts publish their posts in the topic A trapezoid is symmetrical about a vertical center line. If AbhiJ 17 27 Apr 2012, 11:26
7 Experts publish their posts in the topic A symmetric number of an another one is a number where the lucalelli88 9 18 Jan 2010, 02:46
2 500 records have a distribution that is symmetric about the GODSPEED 7 03 Nov 2008, 00:21
Which point is symmetric with point (-5,-2) about the line Ethan 2 28 Mar 2006, 07:18
please explain caribcon 4 11 Dec 2004, 18:07
Display posts from previous: Sort by

Symmetric Problem...Akamai..Please explain

  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®.