Last visit was: 19 Nov 2025, 22:28 It is currently 19 Nov 2025, 22:28
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
User avatar
banerjeea_98
Joined: 18 Nov 2004
Last visit: 17 May 2012
Posts: 676
Own Kudos:
Posts: 676
Kudos: 201
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
Folaa3
Joined: 27 Dec 2004
Last visit: 14 Apr 2006
Posts: 382
Own Kudos:
Posts: 382
Kudos: 128
Kudos
Add Kudos
Bookmarks
Bookmark this Post
avatar
HongHu
Joined: 03 Jan 2005
Last visit: 25 Apr 2011
Posts: 966
Own Kudos:
Posts: 966
Kudos: 796
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
MA
Joined: 25 Nov 2004
Last visit: 09 Aug 2011
Posts: 697
Own Kudos:
Posts: 697
Kudos: 515
Kudos
Add Kudos
Bookmarks
Bookmark this Post
HongHu
I got (C) too. .............................Hopefully I have not confused everybody. :-D 4(k-1)


C. agreed with hong's good explanation.
User avatar
banerjeea_98
Joined: 18 Nov 2004
Last visit: 17 May 2012
Posts: 676
Own Kudos:
Posts: 676
Kudos: 201
Kudos
Add Kudos
Bookmarks
Bookmark this Post
HongHu
I got (C) too.

Can't derive everything by algebra though.

(I) n=4k+3 not sufficient for there are more than one bt (100,120)
(II) n=5m+2 not sufficient for there are more than one bt (100,120)

Combine, I got the idea that these two can only have a common number every 20(=4*5) numbers, so would only have one in (100,120). However I can't express it, so I had to write out the numbers.

Ok I just got an idea:

n=4k+3=5m+2
4k=5m-1=5(m-1)+5-1=5(m-1)+4
4(k-1)=5(m-1)
In other words, k-1 must be divisible by 5. k-1=5t
n=4k+3=4(k-1)+4+3=20t+7

You can get that only one number falls into (100,120), which is 107.

This method though, is more time consuming than writing the numbers out. It is nontherless helpful to us now to understand how to use algebra to derive things.

Hopefully I have not confused everybody. :-D
4(k-1)


Very good, I prefer ur other method, I always get lost when I have to pick numbers in a big range, I keep thinking that I might be missing something, if we can do using algebra, it is quicker and fool-proof. Good job !
User avatar
anirban16
Joined: 24 Jan 2005
Last visit: 20 Jun 2005
Posts: 141
Own Kudos:
Location: Boston
Posts: 141
Kudos: 68
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Here is how I'd hit the problem

(I) ==> n=4k+3 where k=25,26,27,28,29 since 100<n<120
So n= 103,107,111,115,119 : 5 choices not sufficient hence eliminates A and D

(II) ==> n=5k + 2 where k= 20,21,22,
So n = 102,107,112,117 : 4 choices not sufficient eliminated B and D (already eliminated from (I))

No common n from (I) and (II) hence eliminates C.
so we are left with E.

Thanks,
Anirban
User avatar
anirban16
Joined: 24 Jan 2005
Last visit: 20 Jun 2005
Posts: 141
Own Kudos:
Location: Boston
Posts: 141
Kudos: 68
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Sorry it is 107 I overlooked it.
Hence C
Anirban



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Data Sufficiency (DS) Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
Moderators:
Math Expert
105390 posts
GMAT Tutor
1924 posts