Register    Login    Search    Rss Feeds

Forums Home » Ask An Instructor » GMAT Math » GMAT Prep Math


 Page 1 of 1 [ 5 posts ] 



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

What is the remainder

Author Message
shady320
 Post subject: What is the remainder
 Post Posted: Sun Aug 14, 2011 5:52 pm 
Offline
Students


Posts: 1
What is the remainder when the positive integer n is divided by the positive integer k, where k>1?

1) n=(k+1)^3

2) K=5
Top 
RonPurewal
 Post subject: Re: What is the remainder
 Post Posted: Mon Aug 15, 2011 3:05 am 
Offline
ManhattanGMAT Staff


Posts: 7146
shady320 wrote:
What is the remainder when the positive integer n is divided by the positive integer k, where k>1?

1) n=(k+1)^3

2) K=5


(1)
multiply out (k+1)^3 = k^3 + 3(k^2) + 3k + 1.
all of these terms are multiples of k (which don't contribute to the remainder upon division by k) except for the last one, so the remainder must be 1.

(2)
there is no information about n, so this statement is insufficient.

so (a).

--

also note that you should be extremely reluctant to pick answer choice (c) on this problem -- that answer choice is a definite “trap answer”. i.e., it's far too easy -- it actually gives you numerical values of the two variables -- and it doesn't make any use of the fact that the question itself is about remainders.
so, if you can eliminate statement 2 (which shouldn't be that hard) and then dismiss (c) as a trap answer, the only choice that's actually left at that point is the correct answer!
Top 
sfbay
 Post subject: Re: What is the remainder
 Post Posted: Fri Aug 26, 2011 12:25 am 
Offline
Forum Guests


Posts: 26
Location: San Francisco
n/k = (k+1)^3 / K
= (k^3 + 1^3) / k
= k^2 + 1/k

remainder of 1

not sure if this would work for all remainders or just lucky cause it is 1 (1^3 = 1)
Top 
mithunsam
 Post subject: Re: What is the remainder
 Post Posted: Fri Aug 26, 2011 11:37 am 
Offline
Course Students


Posts: 76
sfbay wrote:
n/k = (k+1)^3 / K
= (k^3 + 1^3) / k
= k^2 + 1/k

remainder of 1

not sure if this would work for all remainders or just lucky cause it is 1 (1^3 = 1)

Not correct.

(k+1)^3 / K is not (k^3 + 1^3) / k. When you expand, you will get k^3 + 3(k^2) + 3k + 1.
Top 
RonPurewal
 Post subject: Re: What is the remainder
 Post Posted: Sat Sep 03, 2011 9:01 pm 
Offline
ManhattanGMAT Staff


Posts: 7146
mithunsam wrote:
Not correct.

(k+1)^3 / K is not (k^3 + 1^3) / k. When you expand, you will get k^3 + 3(k^2) + 3k + 1.


yes, thanks.

also note that this result is in my post, directly above the incorrect post.

read the thread, people!
Top 
Display posts from previous:  Sort by  
 
 Page 1 of 1 [ 5 posts ] 





Who is online

Users browsing this forum: No registered users and 0 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: