Register    Login    Search    Rss Feeds

Forums Home » Ask An Instructor » GMAT Math » Manhattan GMAT CAT Math


 Page 1 of 1 [ 7 posts ] 



  Print view Print view Previous topic Previous topic | Next topic Next topic
 

Help : Quant question from Manhattan CAT

Author Message
svshaha
 Post subject: Help : Quant question from Manhattan CAT
 Post Posted: Sun Dec 11, 2011 6:11 am 
Offline
Students


Posts: 3
Hi Guys,

Need help in solving following question :
How many factors does 362 have?
2
8
24
25
26


The correct answer is D: 25

Can anyone please explain how come answer is 25?

Thanks in advance!!!
Top 
tim
 Post subject: Re: Help : Quant question from Manhattan CAT
 Post Posted: Tue Dec 13, 2011 2:50 am 
Online
ManhattanGMAT Staff


Posts: 2242
Location: Southwest Airlines, seat 21C
Before we help with this question, we need you to show some effort of your own. What did you try on this question? Where did you get stuck?

_________________
Tim Sanders
Manhattan GMAT Instructor
Top 
Rijul Negi
 Post subject: Re: Help : Quant question from Manhattan CAT
 Post Posted: Tue Dec 13, 2011 4:15 am 
Offline
Students


Posts: 5
svshaha wrote:
Hi Guys,

Need help in solving following question :
How many factors does 362 have?
2
8
24
25
26


The correct answer is D: 25

Can anyone please explain how come answer is 25?

Thanks in advance!!!



Hi
Are you sure the no is 362? or is their something wrong in what i am doing?

When we need to find the total no of factors
what we usually do is
first convert the number into multiples of prime factors

in this case
362 = 2 * 181 [181 is a prime no]

The total no of factors would be (1+1)*(1+1) = 4
which is not in the options


What happens is
let us say we have a no z
z = a^m * b^n * c^p
here a,b and c are prime nos

when we need to select a factor.. we can choose any power of a from 0 to m
same for b=> 0 to n and for c => 0 to p

the total no of ways of selecting a factor can be rephrased as total no of factors of z => (m+1)(n+1)(p+1)


Last edited by Rijul Negi on Thu Dec 15, 2011 2:15 am, edited 1 time in total.

Top 
svshaha
 Post subject: Re: Help : Quant question from Manhattan CAT
 Post Posted: Wed Dec 14, 2011 4:43 pm 
Offline
Students


Posts: 3
Thanks guys for your messages and I must apologies for my ignorance.

It’s 36^2 (36 raise to 2) not 362.

I would solve it by normal method :
36 * 36 = 1296
1 1296
2 648
3 432
And so on..

During test, solving this questions by above method would be time consuming. So any faster way to solve this question would be helpful.
Top 
Rijul Negi
 Post subject: Re: Help : Quant question from Manhattan CAT
 Post Posted: Thu Dec 15, 2011 2:29 am 
Offline
Students


Posts: 5
svshaha wrote:
Thanks guys for your messages and I must apologies for my ignorance.

It’s 36^2 (36 raise to 2) not 362.

I would solve it by normal method :
36 * 36 = 1296
1 1296
2 648
3 432
And so on..

During test, solving this questions by above method would be time consuming. So any faster way to solve this question would be helpful.



I have mentioned it in my previos post...Check out my previous post..

36^2 = (3^2 x 2^2)^2 = 3^4 * 2^4

Total no of factors = (4+1)*(4+1) = 25
Top 
svshaha
 Post subject: Re: Help : Quant question from Manhattan CAT
 Post Posted: Thu Dec 15, 2011 4:04 am 
Offline
Students


Posts: 3
Thanks a lot Rijul!!! That was really helpful.
Top 
jnelson0612
 Post subject: Re: Help : Quant question from Manhattan CAT
 Post Posted: Mon Dec 26, 2011 12:13 am 
Offline
ManhattanGMAT Staff


Posts: 1857
Very nice Rijul!

_________________
Jamie Nelson
ManhattanGMAT Instructor
Top 
Display posts from previous:  Sort by  
 
 Page 1 of 1 [ 7 posts ] 





Who is online

Users browsing this forum: No registered users and 2 guests

 
 

 
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to: