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.

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Re: prime factors of n [#permalink]
04 Sep 2008, 02:42

Answer is B.

From stmt 1, N is a multiple of 5 in such that N is obtained by multiplying 5 with another prime number.

Thus, N can be 10, 15, 25, 35, 55...... i.e. N can have 1 prime factor (e.g. 25) or 2 (e.g. 10, 15,...)....hence not sufficient.

From stmt2, 3 is already a prime factor. Hence, in order for 3N^2 to have two different prime factor, N^2 has to be a perfect square of a prime number. This implies that N itself is a prime number and hence will have only one prime factor. Hence, sufficient.

Re: prime factors of n [#permalink]
04 Sep 2008, 04:46

arjtryarjtry wrote:

How many prime factors does positive integer N have? (1) N/5 is a prime number. (2) 3N^2 has two different prime number.

D.

If N/5 is a prime number, then N=5*x where x is a prime number. So N has only two prime factors.

if 3*N^2 has two different prime factors, then 3 is one of them and N is the other. In this case, N has to be a prime number and hence will have only one prime factor

Re: prime factors of n [#permalink]
04 Sep 2008, 04:52

IMO C.

1) N = 5a, where a is any prime number. N can have one or two prime factors. Not sufficient 2) 3N^2 has two different prime factors. Not sufficient, because N can have one prime factor, or two prime factors (f.ex. N=21=3*7).

Combine both - N can be 25 or 15, i.e. two prime factors. _________________

Re: prime factors of n [#permalink]
04 Sep 2008, 07:03

arjtryarjtry wrote:

How many prime factors does positive integer N have? (1) N/5 is a prime number. (2) 3N^2 has two different prime number.

(1) N/5 is a prime number. N= 5* x it doesn't matter.. whether x=5 or 3 .. N has two prime factors. N=5*5 ( two prime factors.... though not two different prime factors.)

Question is How many prime factors does positive integer N have? Ans 2

(2) 3N^2 has two different prime number.[/ N must be prime number. sufficient.

D.

If question Says How many different prime factors does positive integer N have? then Ans would be C. _________________

Your attitude determines your altitude Smiling wins more friends than frowning

Re: prime factors of n [#permalink]
04 Sep 2008, 07:24

x2suresh wrote:

arjtryarjtry wrote:

How many prime factors does positive integer N have? (1) N/5 is a prime number. (2) 3N^2 has two different prime number.

(1) N/5 is a prime number. N= 5* x it doesn't matter.. whether x=5 or 3 .. N has two prime factors. N=5*5 ( two prime factors.... though not two different prime factors.)

Question is How many prime factors does positive integer N have? Ans 2

(2) 3N^2 has two different prime number.[/ N must be prime number. sufficient.

D.

If question Says How many different prime factors does positive integer N have? then Ans would be C.

another good catch gosh... hopefully the real test will leave no room for ambiguity .

Re: prime factors of n [#permalink]
04 Sep 2008, 22:50

Nerdboy wrote:

IMO C.

1) N = 5a, where a is any prime number. N can have one or two prime factors. Not sufficient 2) 3N^2 has two different prime factors. Not sufficient, because N can have one prime factor, or two prime factors (f.ex. N=21=3*7).

Combine both - N can be 25 or 15, i.e. two prime factors.

Guys, I messed up completely. If N can be 25 or 15, then answer is E - assuming we are looking for different prime factors. If we are looking for number of prime factors, not necessarily different, then it should be A. OA? _________________

Re: prime factors of n [#permalink]
04 Sep 2008, 23:26

While I await the OA....I have one question here.

If I take the number 25, do I say, it has two prime factors? does it not have only one prime factor and that is 5? 25 can be divided by 5 and 5 is a prime factor. why do I have to count 5 again?

gmatclubot

Re: prime factors of n
[#permalink]
04 Sep 2008, 23:26