It is currently 24 Sep 2017, 18:06

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

PS question

  post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Senior Manager
Senior Manager
avatar
Joined: 29 Aug 2005
Posts: 272

Kudos [?]: 69 [0], given: 0

PS question [#permalink]

Show Tags

New post 03 Jun 2008, 22:48
00:00
A
B
C
D
E

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.

How do i solve these type of questions

can u please explain me the technique
Attachments

book.doc [27 KiB]
Downloaded 161 times

To download please login or register as a user


_________________

The world is continuous, but the mind is discrete

Kudos [?]: 69 [0], given: 0

Senior Manager
Senior Manager
avatar
Joined: 29 Aug 2005
Posts: 272

Kudos [?]: 69 [0], given: 0

Re: PS question [#permalink]

Show Tags

New post 03 Jun 2008, 23:15
alpha_plus_gamma wrote:
vdhawan1 wrote:
How do i solve these type of questions

can u please explain me the technique


Is the answer C.16?



yes the answer is 16

but can u please elaborate how u got to this answer
_________________

The world is continuous, but the mind is discrete

Kudos [?]: 69 [0], given: 0

Manager
Manager
avatar
Joined: 03 Jun 2008
Posts: 134

Kudos [?]: 45 [0], given: 0

Schools: ISB, Tuck, Michigan (Ross), Darden, MBS
Re: PS question [#permalink]

Show Tags

New post 03 Jun 2008, 23:40
vdhawan1 wrote:
How do i solve these type of questions

can u please explain me the technique


Ans. For such questions plz follow the following technique.

The number of factors for a number say X is always equal to (a+1)(b+1)(c+1)..., where a,b,c,.. denote the power of the prime numbers that make this number.

Eg. 50 = 5 (Squared) * 2, here the prime numbers are 5 and 2, and their powers are 2 and 1 respectively. So a and b in this case are 2 and 1.

No of Factors of 50 = (2+1)(1+1) = 6

Similarly for ur question N, has 4 prime numbers as its factors.

Therefore number of Factors for N = (a+1)(b+1)(c+1)(d+1), given the options, a,b,c,d cannot take any other values except 1. SO the ans is 16.

Let me know if this is still not clear.
_________________

-----------------------------------------------------------
'It's not the ride, it's the rider'

Kudos [?]: 45 [0], given: 0

1 KUDOS received
Manager
Manager
avatar
Joined: 28 May 2008
Posts: 93

Kudos [?]: 10 [1], given: 0

Re: PS question [#permalink]

Show Tags

New post 03 Jun 2008, 23:43
1
This post received
KUDOS
vdhawan1 wrote:
How do i solve these type of questions

can u please explain me the technique

It is 16.

I ll show you by an example
lets say the number = 2*3*5*7
we need to find factors.
clearly 1,2,3,5,7 are the factors. total number=5
now selecting the product 2 numbers at a time 4C2= 6
now selecting the product of 3 nos =4c3 =4
now the number n itself =1
sum it up = 16

There is a shorter methid
If n= a^m * b^n * c^p and so on where a, b, c are the prime factors
then total no of divisors= (m+1)*(n+1)*(p+1)

for eg here 2^1 * 3^1 * 5^1 *7^1
Total no of divisore = (1+1)(1+1)(1+1)(1+1)= 16

cheers !!

Kudos [?]: 10 [1], given: 0

Manager
Manager
User avatar
Joined: 31 Oct 2007
Posts: 55

Kudos [?]: 9 [0], given: 0

Re: PS question [#permalink]

Show Tags

New post 03 Jun 2008, 23:57
I thought 1 wasnt a prime number ?? :roll:

Thanks for the great explanation on factorization though.

Kudos [?]: 9 [0], given: 0

Manager
Manager
avatar
Joined: 28 May 2008
Posts: 93

Kudos [?]: 10 [0], given: 0

Re: PS question [#permalink]

Show Tags

New post 04 Jun 2008, 00:00
snoor wrote:
I thought 1 wasnt a prime number ?? :roll:

Thanks for the great explanation on factorization though.

Hey snoor
Please dont gt confused !
1 is STILL not a prime number.
but 1 sure is a factor of any number, right?
lets say n=2
It has 2 factors , 1 and itself

Kudos [?]: 10 [0], given: 0

Senior Manager
Senior Manager
avatar
Joined: 29 Aug 2005
Posts: 272

Kudos [?]: 69 [0], given: 0

Re: PS question [#permalink]

Show Tags

New post 04 Jun 2008, 00:15
zeenie wrote:
vdhawan1 wrote:
How do i solve these type of questions

can u please explain me the technique

It is 16.

I ll show you by an example
lets say the number = 2*3*5*7
we need to find factors.
clearly 1,2,3,5,7 are the factors. total number=5
now selecting the product 2 numbers at a time 4C2= 6
now selecting the product of 3 nos =4c3 =4
now the number n itself =1
sum it up = 16

There is a shorter methid
If n= a^m * b^n * c^p and so on where a, b, c are the prime factors
then total no of divisors= (m+1)*(n+1)*(p+1)

for eg here 2^1 * 3^1 * 5^1 *7^1
Total no of divisore = (1+1)(1+1)(1+1)(1+1)= 16

cheers !!


thanks for the great explanation
its very clear now
_________________

The world is continuous, but the mind is discrete

Kudos [?]: 69 [0], given: 0

Senior Manager
Senior Manager
avatar
Joined: 29 Aug 2005
Posts: 272

Kudos [?]: 69 [0], given: 0

Re: PS question [#permalink]

Show Tags

New post 04 Jun 2008, 00:17
GMBA85 wrote:
vdhawan1 wrote:
How do i solve these type of questions

can u please explain me the technique


Ans. For such questions plz follow the following technique.

The number of factors for a number say X is always equal to (a+1)(b+1)(c+1)..., where a,b,c,.. denote the power of the prime numbers that make this number.

Eg. 50 = 5 (Squared) * 2, here the prime numbers are 5 and 2, and their powers are 2 and 1 respectively. So a and b in this case are 2 and 1.

No of Factors of 50 = (2+1)(1+1) = 6

Similarly for ur question N, has 4 prime numbers as its factors.

Therefore number of Factors for N = (a+1)(b+1)(c+1)(d+1), given the options, a,b,c,d cannot take any other values except 1. SO the ans is 16.

Let me know if this is still not clear.


Thanks for the great explanation
its clear now
_________________

The world is continuous, but the mind is discrete

Kudos [?]: 69 [0], given: 0

SVP
SVP
avatar
Joined: 04 May 2006
Posts: 1890

Kudos [?]: 1354 [0], given: 1

Schools: CBS, Kellogg
Premium Member
Re: PS question [#permalink]

Show Tags

New post 04 Jun 2008, 00:29
zeenie wrote:
snoor wrote:
I thought 1 wasnt a prime number ?? :roll:

Thanks for the great explanation on factorization though.

Hey snoor
Please dont gt confused !
1 is STILL not a prime number.
but 1 sure is a factor of any number, right?
lets say n=2
It has 2 factors , 1 and itself


I think, it should be confused. Let see the original:

If positive number n is product of 4 different prime numbers, including 1 and n,.

I think,
a. adding 1 and n to the total, so the total is 4 numbers.
b. if the above statement is correct, 1 and n are not necessaryly prime number.

what do you think?
_________________

GMAT Club Premium Membership - big benefits and savings

Kudos [?]: 1354 [0], given: 1

Manager
Manager
avatar
Joined: 28 May 2008
Posts: 93

Kudos [?]: 10 [0], given: 0

Re: PS question [#permalink]

Show Tags

New post 04 Jun 2008, 02:01
sondenso wrote:
zeenie wrote:
snoor wrote:
I thought 1 wasnt a prime number ?? :roll:

Thanks for the great explanation on factorization though.

Hey snoor
Please dont gt confused !
1 is STILL not a prime number.
but 1 sure is a factor of any number, right?
lets say n=2
It has 2 factors , 1 and itself


I think, it should be confused. Let see the original:

If positive number n is product of 4 different prime numbers, including 1 and n,.

I think,
a. adding 1 and n to the total, so the total is 4 numbers.
b. if the above statement is correct, 1 and n are not necessaryly prime number.

what do you think?


Hey there..
you might have to reinterpret that bit of the question stem that says "positive number n is product of 4 different prime numbers, including 1 and n,
After all, a number that is a product of 4 prime numbers cannot be a prime number ! right?
Question not framed well I guess. The factors would include 1 and n.

Kudos [?]: 10 [0], given: 0

CEO
CEO
User avatar
Joined: 29 Mar 2007
Posts: 2554

Kudos [?]: 502 [0], given: 0

Re: PS question [#permalink]

Show Tags

New post 04 Jun 2008, 06:37
vdhawan1 wrote:
How do i solve these type of questions

can u please explain me the technique


Here is how I solved.

XYZW
XYZW

Draw lines from X to the others, repeat for Y, but don't draw to its own and to X (B/c already done).

We get 3+2+1 from this.

Now we also have 4 from X, Y,Z,W alone

So we have 3+2+1+4 now. Don't forget 1 and XYWZ.

Thats --> 3+2+1+4+1+1.

Now the number of groups of 3 is simply 4!/3! --> 4

3+2+1+4+1+1+4 = 16.

Kudos [?]: 502 [0], given: 0

Manager
Manager
avatar
Joined: 28 Apr 2008
Posts: 110

Kudos [?]: 12 [0], given: 0

Re: PS question [#permalink]

Show Tags

New post 14 Nov 2008, 02:18
16

4c1+4c2+4c3+2=16

2 is for n and 1.

4c1 is for each of the prime pactors

4c2 is for any multiple of 2 of the four prime numbers

4c3 is for any multiple of 3 of the prime numbers

hope that helps

Kudos [?]: 12 [0], given: 0

Manager
Manager
avatar
Joined: 14 Oct 2008
Posts: 160

Kudos [?]: 64 [0], given: 0

Re: PS question [#permalink]

Show Tags

New post 14 Nov 2008, 04:23
I agree with Sondenso, this question is not correct. GMAT would never include such ambiguous questions in exam.

Although the method everyone is trying to show here is correct (a+1)(b+1) ... but it doesn't apply to this qs as it stands. Whats the source of this qs vwdhawan1 ? Can you also post the explanation they give as the answer ?

Thanks.

Kudos [?]: 64 [0], given: 0

SVP
SVP
User avatar
Joined: 29 Aug 2007
Posts: 2473

Kudos [?]: 834 [0], given: 19

Re: PS question [#permalink]

Show Tags

New post 14 Nov 2008, 14:15
sondenso wrote:
zeenie wrote:
snoor wrote:
I thought 1 wasnt a prime number ?? :roll:

Thanks for the great explanation on factorization though.

Hey snoor
Please dont gt confused !
1 is STILL not a prime number.
but 1 sure is a factor of any number, right?
lets say n=2
It has 2 factors , 1 and itself


I think, it should be confused. Let see the original:

If positive number n is product of 4 different prime numbers, including 1 and n,.

I think,
a. adding 1 and n to the total, so the total is 4 numbers.
b. if the above statement is correct, 1 and n are not necessaryly prime number.

what do you think?



THE QUESTION SHOULD READ AS UNDER: If positive integer n is the product of 4 different prime numbers, how many factors does n have, including 1 and n,?

two ways to solve it:

1: 4c1+4c2+4c3+4c4 = 16
2: (1+1)(1+1)(1+1)(1+1) = 16
_________________

Verbal: http://gmatclub.com/forum/new-to-the-verbal-forum-please-read-this-first-77546.html
Math: http://gmatclub.com/forum/new-to-the-math-forum-please-read-this-first-77764.html
Gmat: http://gmatclub.com/forum/everything-you-need-to-prepare-for-the-gmat-revised-77983.html


GT

Kudos [?]: 834 [0], given: 19

Manager
Manager
avatar
Joined: 23 Jul 2008
Posts: 194

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

Re: PS question [#permalink]

Show Tags

New post 14 Nov 2008, 17:04
then in that case don t you think the answer shud be 18

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

SVP
SVP
User avatar
Joined: 29 Aug 2007
Posts: 2473

Kudos [?]: 834 [0], given: 19

Re: PS question [#permalink]

Show Tags

New post 14 Nov 2008, 17:23
hibloom wrote:
then in that case don t you think the answer shud be 18


Those are already included in 16. 8-) :-D
_________________

Verbal: http://gmatclub.com/forum/new-to-the-verbal-forum-please-read-this-first-77546.html
Math: http://gmatclub.com/forum/new-to-the-math-forum-please-read-this-first-77764.html
Gmat: http://gmatclub.com/forum/everything-you-need-to-prepare-for-the-gmat-revised-77983.html


GT

Kudos [?]: 834 [0], given: 19

Manager
Manager
avatar
Joined: 23 Jul 2008
Posts: 194

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

Re: PS question [#permalink]

Show Tags

New post 15 Nov 2008, 08:51
should have read carefully it is included

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

Re: PS question   [#permalink] 15 Nov 2008, 08:51
Display posts from previous: Sort by

PS question

  post reply Question banks Downloads My Bookmarks Reviews Important topics  


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