Check GMAT Club Decision Tracker for the Latest School Decision Releases https://gmatclub.com/AppTrack
GMAT Club

 It is currently 27 Mar 2017, 19:54

### 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

Author Message
Manager
Joined: 09 Sep 2004
Posts: 54
Followers: 2

Kudos [?]: 132 [0], given: 0

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

### Show Tags

17 Sep 2004, 00:36
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

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: 2

Kudos [?]: 129 [0], given: 0

### Show Tags

17 Sep 2004, 01:13
n = a^2bcd
Number of factors = (3)(2)(2)(2) = 24?
Manager
Joined: 02 Apr 2004
Posts: 224
Location: Utrecht
Followers: 1

Kudos [?]: 21 [0], given: 0

### Show Tags

17 Sep 2004, 01:34
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: 2

Kudos [?]: 129 [0], given: 0

### Show Tags

17 Sep 2004, 01:37
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: 609
Followers: 3

Kudos [?]: 127 [0], given: 0

### Show Tags

17 Sep 2004, 04:49
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 [?]: 21 [0], given: 0

### Show Tags

17 Sep 2004, 04:59
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: 4302
Followers: 42

Kudos [?]: 451 [0], given: 0

### Show Tags

17 Sep 2004, 08:04
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: Russian Federation
GMAT 1: 710 Q49 V0
GMAT 2: 700 Q V
GMAT 3: 740 Q40 V50
GMAT 4: 700 Q48 V38
GMAT 5: 710 Q45 V41
GMAT 6: 680 Q47 V36
GMAT 7: Q42 V44
GMAT 8: Q42 V44
GMAT 9: 740 Q49 V42
GMAT 10: 740 Q V
GMAT 11: 500 Q47 V33
GMAT 12: 670 Q V
GMAT 13: 680 Q V
GMAT 14: 760 Q49 V44
WE: Supply Chain Management (Energy and Utilities)
Followers: 0

Kudos [?]: 214 [0], given: 103787

### Show Tags

17 Sep 2004, 10:18
Thanks hardworker_indian for the formula and explanation.
17 Sep 2004, 10:18
Display posts from previous: Sort by