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

 It is currently 05 May 2015, 05:53

# Expecting Soon:

Wharton Round 3 Decisions.   |   Join Chat Room for Live Updates

### 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

# A number is a product of 5 prime factors, 2 of them are

 Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:
Manager
Joined: 09 Sep 2004
Posts: 54
Followers: 2

Kudos [?]: 30 [0], given: 0

A number is a product of 5 prime factors, 2 of them are [#permalink]  16 Sep 2004, 23:36
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
A number is a product of 5 prime factors, 2 of them are same. How many factors does it have?
Director
Joined: 20 Jul 2004
Posts: 593
Followers: 1

Kudos [?]: 48 [0], given: 0

[#permalink]  17 Sep 2004, 00:13
n = a^2bcd
Number of factors = (3)(2)(2)(2) = 24?
Manager
Joined: 02 Apr 2004
Posts: 224
Location: Utrecht
Followers: 1

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

[#permalink]  17 Sep 2004, 00:34
Hmmm, I get 18 factors

I used the prime numbers
2 * 2 * 3 * 5 * 7 = 420

I try to made all possible combinations by combining all possible prime numbers.

Please correct me if I am wrong.

Regards,

Alex
Director
Joined: 20 Jul 2004
Posts: 593
Followers: 1

Kudos [?]: 48 [0], given: 0

[#permalink]  17 Sep 2004, 00:37
A number is a product of 5 prime factors, 2 of them are same.
For explanation, I considered these to be a, b, c, d. n = a^2bcd a is reapeted twice.

To find the number of factors, say for x^a.y^b.z^c, simply multiply the powers+1, i.e. no of factors = (a+1)(b+1)(c+1)

In this case, no of factors of a^2bcd = 3.2.2.2 = 24

I learnt this formula from the forum - an old discusion between Stolyar and AkamaiBrah. That said, beware of its use, it can be used only in the simple case.
Director
Joined: 31 Aug 2004
Posts: 606
Followers: 3

Kudos [?]: 43 [0], given: 0

[#permalink]  17 Sep 2004, 03:49
i writed all of them and i obtained 23 factors
+ 1 which is always a factor

1 a b c d a^2 ab ac ad bc bd cd a^2b a^2c a^2d acb adc adb bcd a^2cb a^2dc a^2db abcd a^2bcd

24

Sounds like this formula is working very well... I will use it from now on !
Manager
Joined: 02 Apr 2004
Posts: 224
Location: Utrecht
Followers: 1

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

[#permalink]  17 Sep 2004, 03:59
I did an recount and came also to 24.

I dont know why I came to 18 in the first place!!!

However is it also possible to use some combination theory
2 2 3 5 7 = 5 prime numbers.
2 are the same which can be counted as 1

Therefore 4*3*2*1 = 24 possibilities.

It is correct to use this method???

Regards,

Alex
GMAT Club Legend
Joined: 15 Dec 2003
Posts: 4313
Followers: 27

Kudos [?]: 217 [0], given: 0

[#permalink]  17 Sep 2004, 07:04
hardworker_indian wrote:
A number is a product of 5 prime factors, 2 of them are same.
For explanation, I considered these to be a, b, c, d. n = a^2bcd a is reapeted twice.

To find the number of factors, say for x^a.y^b.z^c, simply multiply the powers+1, i.e. no of factors = (a+1)(b+1)(c+1)

In this case, no of factors of a^2bcd = 3.2.2.2 = 24

I learnt this formula from the forum - an old discusion between Stolyar and AkamaiBrah. That said, beware of its use, it can be used only in the simple case.

Yes, that discussion was gold. I learned it from this forum too.
_________________

Best Regards,

Paul

Joined: 31 Dec 1969
Location: India
Concentration: General Management, Strategy
GMAT 1: 710 Q49 V0
GMAT 2: 740 Q40 V50
GMAT 3: 700 Q48 V38
GPA: 3.6
Followers: 0

Kudos [?]: 89 [0], given: 87146

[#permalink]  17 Sep 2004, 09:18
Thanks hardworker_indian for the formula and explanation.
[#permalink] 17 Sep 2004, 09:18
Similar topics Replies Last post
Similar
Topics:
1 A number N when expressed as product of prime factors gives. 8 06 Oct 2010, 05:07
1 Number Of Prime Factors 2 30 Aug 2010, 15:23
3 PRODUCT OF PRIME NUMBER 2 02 Aug 2009, 05:36
product of prime numbers 3 12 Jun 2009, 20:28
2 Number properties: Prime Factors ... 11 01 Jan 2008, 13:13
Display posts from previous: Sort by

# A number is a product of 5 prime factors, 2 of them are

 Question banks Downloads My Bookmarks Reviews Important topics

 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®.