It is currently 21 Oct 2017, 09:22

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

Math

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Intern
Intern
avatar
Joined: 23 May 2012
Posts: 3

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

Math [#permalink]

Show Tags

New post 05 Nov 2012, 12:28
What is the next number in the series : 5-3-1-7-3-2-9-5-.........

Want proper explanation .........................

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

Expert Post
1 KUDOS received
Magoosh GMAT Instructor
User avatar
G
Joined: 28 Dec 2011
Posts: 4426

Kudos [?]: 8455 [1], given: 102

Re: Math [#permalink]

Show Tags

New post 05 Nov 2012, 19:44
1
This post received
KUDOS
Expert's post
wahedhossain wrote:
What is the next number in the series : 5-3-1-7-3-2-9-5-.........

Want proper explanation .........................

Dear Wahedhossain:

I send you a pm earlier in the day. First of all, this question, while intriguing, is not in standard GMAT format (PS or DS). Second, it's so open-ended --- the GMAT would never ask anything like this.

It's so open-ended --- the trouble is, the longer I stare at it, the more I can imagine various strange bizarre patterns.

Here is one possible pattern:
a) start with an odd number
b) go down to the highest prime number greater than than number's sqaureroot
c) go down the largest factor of the difference a - b that is less than b
d) go up to the next odd number above (a)

That gives 5-3-1-7-3-2-9-5-2-11-5-3-13-5-4.....

Here's another possible pattern:
a) start with 5
b) descend by subtracting 2's
c) when you get as low as you can go, go up to the next highest odd number
d) descend by subtracting 4 & 1 in alternation
e) when you get as low as you can go, go up to the next highest odd number
f) descent by subtracting 4's
g) when you get as low as you can go, go up to the next highest odd number
h) descend by subtracting 6 & 1 in alternation
i) when you get as low as you can go, go up to the next highest odd number
j) descent by subtracting 6's
etc.

5-3-1-7-3-2-9-5-1-11-5-4-13-7-1-......

As you can see, both of these "patterns" are relatively contrived, and I easily could come up with a dozen more. The point is --- there's nothing about the pattern that leaps out and taps into a clear mathematical rule. Because this is given without any context, it makes the choice of isolating one correct pattern from among many just about impossible.

If you could provide more information about the source, about any context, possible answer choices, etc. etc. that would be very helpful.

Mike :-)
_________________

Mike McGarry
Magoosh Test Prep

Image

Image

Kudos [?]: 8455 [1], given: 102

Intern
Intern
avatar
Joined: 23 May 2012
Posts: 3

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

Re: Math [#permalink]

Show Tags

New post 05 Nov 2012, 20:20
Thanks a lot .......................

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

Expert Post
Founder
Founder
User avatar
P
Joined: 04 Dec 2002
Posts: 15590

Kudos [?]: 28530 [0], given: 5114

Location: United States (WA)
GMAT 1: 750 Q49 V42
GMAT ToolKit User Premium Member CAT Tests
Re: Math [#permalink]

Show Tags

New post 05 Nov 2012, 21:23
We'll lock the topic for now since this is not a pure GMAT Question. Thank you Mike for an amazing answer!
_________________

Founder of GMAT Club

Just starting out with GMAT? Start here... or use our Daily Study Plan


Co-author of the GMAT Club tests

Kudos [?]: 28530 [0], given: 5114

Re: Math   [#permalink] 05 Nov 2012, 21:23
Display posts from previous: Sort by

Math

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  

Moderator: HiLine



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®.