It is currently 19 Sep 2017, 06:51

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.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

In the Sequence a1, a2,............a(n),............each

  post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
1 KUDOS received
Director
Director
User avatar
Joined: 04 Jan 2008
Posts: 896

Kudos [?]: 731 [1], given: 17

In the Sequence a1, a2,............a(n),............each [#permalink]

Show Tags

New post 20 Jul 2009, 01:09
1
This post received
KUDOS
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

In the Sequence a1, a2,............a(n),............each term after the first is 3 greater than the previous term. Is a(100)-1 divisible by 3?

(1)a(99) is indivisible by 3

(2)a1=1

OA....
[Reveal] Spoiler:
...........B....OE says..... a99 can be 3n-1 or 3n-2...hence ....INSUFF..i believe its D

_________________

http://gmatclub.com/forum/math-polygons-87336.html
http://gmatclub.com/forum/competition-for-the-best-gmat-error-log-template-86232.html

Kudos [?]: 731 [1], given: 17

Senior Manager
Senior Manager
avatar
Joined: 23 Jun 2009
Posts: 360

Kudos [?]: 133 [0], given: 80

Location: Turkey
Schools: UPenn, UMich, HKS, UCB, Chicago
Re: Sequence--Is a(100) -1 divisible by 3? [#permalink]

Show Tags

New post 20 Jul 2009, 01:40
B
If all terms are greater than the previous terms by three, it means they all have the same value in (mod 3).
1 insuff. Because we do not know the value of a(99) in (mod 3). It may be 1 or 2. Each choice changes the answer.
2 suff. Since all the terms have same value in (mod 3), a(1)=a(100)=1 in (mod 3). So a(100)-1 is divisible.

Kudos [?]: 133 [0], given: 80

Director
Director
User avatar
Joined: 04 Jan 2008
Posts: 896

Kudos [?]: 731 [0], given: 17

Re: Sequence--Is a(100) -1 divisible by 3? [#permalink]

Show Tags

New post 20 Jul 2009, 01:42
maliyeci wrote:
1 insuff. Because we do not know the value of a(99) in (mod 3). It may be 1 or 2. Each choice changes the answer.


got it now
a(99) is 1 or 2

so a(100) becomes 4 or 6

so a(100)-1 becomes 3 or 5


hence INSUFF.
thanks
_________________

http://gmatclub.com/forum/math-polygons-87336.html
http://gmatclub.com/forum/competition-for-the-best-gmat-error-log-template-86232.html

Kudos [?]: 731 [0], given: 17

Manager
Manager
avatar
Joined: 07 Apr 2009
Posts: 145

Kudos [?]: 13 [0], given: 3

Re: Sequence--Is a(100) -1 divisible by 3? [#permalink]

Show Tags

New post 20 Jul 2009, 13:45
Quote:
If all terms are greater than the previous terms by three, it means they all have the same value in (mod 3).


hey can you please throw some light on this statement.

Kudos [?]: 13 [0], given: 3

Senior Manager
Senior Manager
avatar
Joined: 23 Jun 2009
Posts: 360

Kudos [?]: 133 [0], given: 80

Location: Turkey
Schools: UPenn, UMich, HKS, UCB, Chicago
Re: Sequence--Is a(100) -1 divisible by 3? [#permalink]

Show Tags

New post 21 Jul 2009, 00:03
OK.
a(1)=1, a(2)=4, a(3)=7......a(n)=a(n-1)+3
a(1)=1 in (mod 3)
a(2)=4=1 in mod (3)
a(3)=7=4=1 in mod(3)
For every term you add 3 to previous term. This means in (mod 3) you add a "0" (3 is equal to 0 in mod 3) so every term in this sequence is equal to 1 ;) This is true for other cases (2 and 0)

Kudos [?]: 133 [0], given: 80

Manager
Manager
avatar
Joined: 07 Apr 2009
Posts: 145

Kudos [?]: 13 [0], given: 3

Re: Sequence--Is a(100) -1 divisible by 3? [#permalink]

Show Tags

New post 21 Jul 2009, 04:54
sure thanks ! i think i got it !

Kudos [?]: 13 [0], given: 3

Re: Sequence--Is a(100) -1 divisible by 3?   [#permalink] 21 Jul 2009, 04:54
Display posts from previous: Sort by

In the Sequence a1, a2,............a(n),............each

  post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

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®.