It is currently 24 Nov 2017, 04:32

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Math

Author Message
TAGS:

### Hide Tags

Intern
Joined: 23 May 2012
Posts: 3

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

### Show Tags

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

Magoosh GMAT Instructor
Joined: 28 Dec 2011
Posts: 4503

Kudos [?]: 8790 [1], given: 106

### Show Tags

05 Nov 2012, 19:44
1
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:
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:
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.

Mike
_________________

Mike McGarry
Magoosh Test Prep

Education is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)

Kudos [?]: 8790 [1], given: 106

Intern
Joined: 23 May 2012
Posts: 3

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

### Show Tags

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

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

Founder
Joined: 04 Dec 2002
Posts: 15884

Kudos [?]: 29121 [0], given: 5273

Location: United States (WA)
GMAT 1: 750 Q49 V42

### Show Tags

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 [?]: 29121 [0], given: 5273

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

# Math

Moderator: HKD1710

 HOT DEALS FOR NOVEMBER Economist GMAT - Free Free 1-week trial + Free Test Kaplan Courses - Save \$475 \$225 Discount + \$250 Bonus Target Test Prep - \$800 \$50 Discount + \$750 Bonus [GMAT ClubTests and Premium MBA Bundle] EMPOWERgmat - \$99/mo GMAT Club tests included 2nd month GMAT Club Tests - Free Included with every course purchaseof \$149 or more - Full List is here

 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®.