GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 16 Aug 2018, 01:11

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

For any positive integer n, the length of n

  post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Manager
Manager
avatar
Joined: 05 Aug 2008
Posts: 88
Schools: McCombs Class of 2012
For any positive integer n, the length of n  [#permalink]

Show Tags

New post 19 Dec 2008, 17:05
For any positive integer n, the length of n is defined as the number of prime factors whose product is n. For example, the length of 75 is 3, since 75 = 3 x 5 x 5. How many two-digit positive integers have a length of 6?

(A) None
(B) One
(C) Two
(D) Three
(E) Four


Can someone please give me an approach to how to solve this kind of problem?

thank you.
Attachment:
Q1.JPG
Q1.JPG [ 25.2 KiB | Viewed 964 times ]


--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Senior Manager
Senior Manager
User avatar
Joined: 21 Apr 2008
Posts: 265
Location: Motortown
Re: Prime factors  [#permalink]

Show Tags

New post 19 Dec 2008, 17:40
1
Before I go ahead, it looks like you have selected A:None and the answer is C:TWO.

I am not too sure whether you have understood the concept of prime factors. I will explain it anyway, just to refresh my memory. :)

'Prime factors are prime numbers that divide an integer, without leaving a remainder'
eg: 6 = 2 * 3, so 6 has TWO prime factors.

Now coming to the problem here, it is asking us to find integers starting from 11 to 99 that can be divided by 6 prime factors(all of them could be same or different)

Lets pick the smallest of all : 2
1. 2^6 = 2*2*2*2*2*2 = 64 - ONE

Lets use 2 and 3 now
2. 2^5 *3 = 2*2*2*2*2*3 = 96 - TWO

Now lets try to use 4 2's and 2 3's
2*2*2*2*3*3 = 144

That means, we can't go any further.

So, the answer has to be C: TWO
Manager
Manager
avatar
Joined: 05 Aug 2008
Posts: 88
Schools: McCombs Class of 2012
Re: Prime factors  [#permalink]

Show Tags

New post 19 Dec 2008, 18:06
Thanks, LiveStronger.

thank you for the excellent explanation. I couldn't think of a solid approach to the problem when I got to it on my practice test. Didn't even think about starting with the lowest prime!!:)

thanks again.

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Re: Prime factors &nbs [#permalink] 19 Dec 2008, 18:06
Display posts from previous: Sort by

For any positive integer n, the length of n

  post reply Question banks Downloads My Bookmarks Reviews Important topics  

Moderator: chetan2u

Events & Promotions

PREV
NEXT


GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| 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®.