Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 22 May 2015, 19:08

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# very hard ds question

 Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:
Manager
Joined: 11 Nov 2007
Posts: 61
Followers: 1

Kudos [?]: 5 [0], given: 0

very hard ds question [#permalink]  14 Dec 2007, 23:25
00:00

Difficulty:

(N/A)

Question Stats:

100% (02:56) correct 0% (00:00) wrong based on 2 sessions
if m and n are both 2-digit numbers, and m-n=11x, is x an integer?
1. the tens digit and the units digit of m are the same
2. m+n is a multiple of 11.

OA ******************

***************
is C
 Kaplan GMAT Prep Discount Codes Knewton GMAT Discount Codes Manhattan GMAT Discount Codes
SVP
Joined: 29 Aug 2007
Posts: 2496
Followers: 58

Kudos [?]: 562 [0], given: 19

Re: very hard ds question [#permalink]  15 Dec 2007, 00:15
aliensoybean wrote:
if m and n are both 2-digit numbers, and m-n=11x, is x an integer?
1. the tens digit and the units digit of m are the same
2. m+n is a multiple of 11.

Since m - n = 11x, is x an integer?

1. m = aa means m is divisible by 11, but n = ? do not know.
2. m+n = 11x, do not m and n each alone.

togather: since m is aa, and m+n = 11x, then n must be also divisible by 11. so suff.

C.

CEO
Joined: 17 Nov 2007
Posts: 3577
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
Followers: 408

Kudos [?]: 2168 [0], given: 359

[#permalink]  15 Dec 2007, 00:23
Expert's post
C

1. we don't know n.INSUFF

2. m+n=11k. There are two patterns for reminders of m and n: (0,0) and (r,11-r), where 0<r<11.

So, for (0,0) m-n=11s, for (r,11-r): (m-n)(mod 11)=r-11+r=2r but 2r<>0 and 2r<>11. ISUFF.

1&2. from 1. m=AA=A*10+A=11*A. So, from 2 we have only one pattern: (0,0). SUFF.
Manager
Joined: 11 Nov 2007
Posts: 61
Followers: 1

Kudos [?]: 5 [0], given: 0

[#permalink]  15 Dec 2007, 13:34
Tiger,
1. m = aa means m is divisible by 11, but n = ? do not know.

If m = aa, doesn't that force n to be a mutiple of 11 since the original equation says that m-n is a multiple of 11. Ex: m=55-n=11X, n = bb, so is a multiple of 11, which means X is an integer
CEO
Joined: 29 Mar 2007
Posts: 2589
Followers: 16

Kudos [?]: 238 [0], given: 0

Re: very hard ds question [#permalink]  15 Dec 2007, 22:26
aliensoybean wrote:
if m and n are both 2-digit numbers, and m-n=11x, is x an integer?
1. the tens digit and the units digit of m are the same
2. m+n is a multiple of 11.

OA ******************

***************
is C

Ive stopped using Kaplan for this reason. While the problems can be decent practice, the explanations are terrible. Its like someone hurried up to write them so he/she could hurry up to go to party or somethin. Just poorly done.

Anyway:

2 is easier so i started w/ it.

2: (m+n)/11 --> Could be 12+10 22/11 12-10 =2. So X is not an integer. b/c 11x=2 --> x=2/11

Then we could have 66+33 --> 99/11 66-33 =33 X=3 so x is an integer.

1: Doesnt help us at all.

Together: the only way for m+n to be divisble by 11 is to have both integers divisible by 11. This means that their sum or difference is ALSO divisible by 11.

So C.
SVP
Joined: 29 Aug 2007
Posts: 2496
Followers: 58

Kudos [?]: 562 [0], given: 19

[#permalink]  15 Dec 2007, 23:06
aliensoybean wrote:
Tiger,
1. m = aa means m is divisible by 11, but n = ? do not know.

If m = aa, doesn't that force n to be a mutiple of 11 since the original equation says that m-n is a multiple of 11. Ex: m=55-n=11X, n = bb, so is a multiple of 11, which means X is an integer

m - n = 11x, but we do not know whether x is an integer. in fact thats the question.

suppose, m = 44 and n = 14, then m - n = 30
so 30 = 11x
x = 30/11, which is not an integer

if n = 22, then m-n = 44-22=22,
22 = 11x
x = 2, which is an integer.

therefore, 1 is not suff.
[#permalink] 15 Dec 2007, 23:06
Similar topics Replies Last post
Similar
Topics:
1 NEED HARD DS questions for practice. 6 26 Aug 2011, 08:38
Finding Gmatclub Tests very hard 9 04 Sep 2010, 17:04
ds - hard 1 10 Dec 2007, 05:21
HARD DS Number Properties:( 3 06 Aug 2006, 14:37
Need advices, I am still weak on very hard verbal questions? 0 19 Jul 2005, 05:16
Display posts from previous: Sort by

# very hard ds question

 Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group and phpBB SEO 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®.