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

It is currently 18 Sep 2014, 20:20

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

NUMBER THEORY

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
avatar
Joined: 04 Sep 2006
Posts: 117
Followers: 2

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

NUMBER THEORY [#permalink] New post 02 Feb 2009, 10:38
* Please, don't capitalize your posts* Walker

Q : N IS AN INTEGER FROM 1 TO 99 INCLUSIVVE WHAT IS THE PROB THAT N(N+1) IS DIVISIBLE BY 3 ?
CEO
CEO
User avatar
Joined: 29 Aug 2007
Posts: 2501
Followers: 53

Kudos [?]: 506 [0], given: 19

GMAT Tests User
Re: NUMBER THEORY [#permalink] New post 02 Feb 2009, 11:31
vcbabu wrote:
Q : N IS AN INTEGER FROM 1 TO 99 INCLUSIVVE WHAT IS THE PROB THAT N(N+1) IS DIVISIBLE BY 3 ?


if n = 1, n(n+1) = 1x2 ...... not divisible.
if n = 2, n(n+1) = 2x3 ...... divisible.
if n = 3, n(n+1) = 3x4 ...... divisible.
if n = 4, n(n+1) = 4x5 ...... not divisible.
if n = 5, n(n+1) = 5x6 ...... divisible.
if n = 6, n(n+1) = 6x7 ..... divisible.
if n = 7, n(n+1) = 7x8 ...... not divisible.


so on.

the pattren is 2 out of 3 is divisible by 3. so the prob = 2/3 or 66.67%.
_________________

Verbal: new-to-the-verbal-forum-please-read-this-first-77546.html
Math: new-to-the-math-forum-please-read-this-first-77764.html
Gmat: everything-you-need-to-prepare-for-the-gmat-revised-77983.html


GT

1 KUDOS received
Senior Manager
Senior Manager
avatar
Joined: 30 Nov 2008
Posts: 494
Schools: Fuqua
Followers: 10

Kudos [?]: 123 [1] , given: 15

GMAT Tests User
Re: NUMBER THEORY [#permalink] New post 02 Feb 2009, 12:10
1
This post received
KUDOS
Agree that the prpbability is 2/3. If we have to go by probability theory, then here is my approach.

Total no of numbers between 1 - 99 = 99.
Event is picking a number whose n(n+1) is divisible by 3 which means either n should be divisible by 3 or n+1 is divisible by 3.
Total Number of numbers from 1 to 99 divisisible by 3 is 33.
Total number of number from 1 to 99 where n+1 is divisible by 3 is also 33.

Probability = No of possible events / total number of events = 66 / 99 = 2/3.
Re: NUMBER THEORY   [#permalink] 02 Feb 2009, 12:10
    Similar topics Author Replies Last post
Similar
Topics:
1 Experts publish their posts in the topic If n is an integer and n^3 is divisible by 24, what is the largest num anik89 2 17 Sep 2014, 23:56
1 Experts publish their posts in the topic Number theory..... pzazz12 3 05 Oct 2010, 04:39
NUMBER THEORY vcbabu 5 03 Feb 2009, 10:11
number properties/number theory gmatiscoming 0 20 May 2007, 18:06
GmatPrep - Number Theory tl372 10 15 Jun 2006, 03:21
Display posts from previous: Sort by

NUMBER THEORY

  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®.