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

It is currently 24 Oct 2014, 10:57

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

Prime Boxes

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Intern
Intern
avatar
Joined: 29 Apr 2011
Posts: 5
Location: India
Schools: Top 20
Followers: 1

Kudos [?]: 0 [0], given: 1

Prime Boxes [#permalink] New post 29 Apr 2011, 23:20
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

100% (00:00) correct 0% (00:00) wrong based on 1 sessions
Hi Friends

I just began my preparation by starting off with Manahattan GMAT "The Number Properties Book", in it he did explain the concept of a prime box.As it states, a box that contains all the prime factors of any number is a prime box. It helps us to find out whether a giver no is a factor of another no or not.Okie, I have a doubt here, I understood what a prime box was and how to make a prime box for a specific number. But I have this new, using primebox is the only way to solve problems related to this stuff? or can we do it by any general procedure?..I thereby request any one explain me about the alternative procedure, if available...


The question was
If 80 is a factor of r,is 15 a factor of r?



regards
SVA
Kaplan GMAT Prep Discount CodesKnewton GMAT Discount CodesManhattan GMAT Discount Codes
Manager
Manager
avatar
Joined: 09 Aug 2010
Posts: 107
Followers: 1

Kudos [?]: 20 [0], given: 7

Re: Prime Boxes [#permalink] New post 30 Apr 2011, 02:47
Quote:
If 80 is a factor of r,is 15 a factor of r?


Enumerate the prime numbers of 80 ==>
2x2x2x2x5

If 80 is a factor of r, then
r = 2x2x2x2x5x(...)

The (...) means we don't know if there are any other integers in r.
Quote:
So two possibilities,
1) No other prime numbers in r
2) There are other prime numbers. It could be 3. It could be not.

Since we are not certain..

15 may or may not be a factor of r. CANNOT DETERMINE!
Math Forum Moderator
avatar
Joined: 20 Dec 2010
Posts: 2037
Followers: 128

Kudos [?]: 956 [0], given: 376

Re: Prime Boxes [#permalink] New post 30 Apr 2011, 03:19
svagmat wrote:
Hi Friends

I just began my preparation by starting off with Manahattan GMAT "The Number Properties Book", in it he did explain the concept of a prime box.As it states, a box that contains all the prime factors of any number is a prime box. It helps us to find out whether a giver no is a factor of another no or not.Okie, I have a doubt here, I understood what a prime box was and how to make a prime box for a specific number. But I have this new, using primebox is the only way to solve problems related to this stuff? or can we do it by any general procedure?..I thereby request any one explain me about the alternative procedure, if available...


The question was
If 80 is a factor of r,is 15 a factor of r?

regards
SVA


Prime factorization is the best method I know for these types of problem and I strongly recommend everyone to get acquainted with it.

For 15 to be a factor of r; r should contain at least as many factors as 15 has.

15=3*5
r must contain at least one 3 and one 5 as its factor to be a qualified multiple of 15.

80=2*2*2*2*5
This tells us that r contains at least four 2's and one 5 as its factors. But, we need just one 2 and one 3. We have one 2 but we don't know whether r contains 3. It may or may not contain 3. Thus, we won't know whether r is a multiple of 15 OR 15 is a factor of r.

e.g.
r=80=2*2*2*2*5. Not divisible by 15(No 3 in 80)
r=160=2*2*2*2*5. Not divisible by 15(No 3 in 160)
r=240=2*2*2*2*5*3. Divisible by 15(as now we have one 2 and one 3 in 240)
r=320=2*2*2*2*5*2*2. Not Divisible by 15(No 3 in 320)
r=400=2*2*2*2*5*5. Not Divisible by 15(No 3 in 400)
r=480=2*2*2*2*5*2*3. Divisible by 15(as now we have one 2 and one 3 in 480)

Conclusion:
In order for r to be a multiple 15, r should be a multiple of 3 as well in addition to be a multiple of 80.
_________________

~fluke

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Intern
Intern
avatar
Joined: 29 Apr 2011
Posts: 5
Location: India
Schools: Top 20
Followers: 1

Kudos [?]: 0 [0], given: 1

Re: Prime Boxes [#permalink] New post 30 Apr 2011, 16:38
Thanks a lott fluke and lawschoolsearcher..That definitely cleared my doubt..


regards
SVA
Re: Prime Boxes   [#permalink] 30 Apr 2011, 16:38
    Similar topics Author Replies Last post
Similar
Topics:
Box sher676 2 31 Jul 2009, 16:01
box area to box volume GGUY 3 14 Apr 2009, 04:41
the championship on boxing matematikconsultant 9 17 Feb 2009, 12:34
Box shipment spiridon 14 15 Oct 2008, 13:08
The figure is a box within a box. Imagine a photograph hilairity 1 22 Dec 2004, 11:22
Display posts from previous: Sort by

Prime Boxes

  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®.