GMAT Changed on April 16th - Read about the latest changes here

It is currently 26 May 2018, 16:24

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If x is a positive integer, is (10x - 1) divisible by y

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

1 KUDOS received
Intern
Intern
avatar
Joined: 08 May 2014
Posts: 10
Concentration: General Management, Operations
GMAT ToolKit User
If x is a positive integer, is (10x - 1) divisible by y [#permalink]

Show Tags

New post 14 Nov 2014, 10:35
1
This post received
KUDOS
2
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  65% (hard)

Question Stats:

46% (01:28) correct 54% (01:19) wrong based on 83 sessions

HideShow timer Statistics

If x is a positive integer, is (10x - 1) divisible by y

(1) x is a multiple of y
(2) y is a prime number
1 KUDOS received
Manager
Manager
avatar
Joined: 23 Oct 2012
Posts: 53
GMAT ToolKit User
Re: If x is a positive integer, is (10x - 1) divisible by y [#permalink]

Show Tags

New post 14 Nov 2014, 23:08
1
This post received
KUDOS
prakash85 wrote:
If x is a positive integer, is (10x - 1) divisible by y

(1) x is a multiple of y
(2) y is a prime number


Q asks (10x-1)/y

1) x/y
x=3 , y=0.5 yes
x=4, y=2 no
insufficient

2) y is a prime number.
insufficient

1+ 2

x=4, y=2 no

x=10, y=5 no

x=20, y = 4 no

sufficient.

Thus, OA is C.
_________________

Kudos please!

Expert Post
Director
Director
User avatar
B
Affiliations: GMATQuantum
Joined: 19 Apr 2009
Posts: 605
Re: If x is a positive integer, is (10x - 1) divisible by y [#permalink]

Show Tags

New post 14 Nov 2014, 23:51
I would suggest that a proper GMAT question on divisibility will constrain y to be an integer. I have never seen a GMAT question that is related to factors and divisibility where a variable could be a real number.

The modified question should look like:
If x and y are positive integers, is (10x - 1) divisible by y ?

(1) x is a multiple of y
(2) y is a prime number

Cheers,
Dabral
Manager
Manager
avatar
Joined: 22 Sep 2012
Posts: 140
Concentration: Strategy, Technology
WE: Information Technology (Computer Software)
Re: If x is a positive integer, is (10x - 1) divisible by y [#permalink]

Show Tags

New post 15 Nov 2014, 09:00
Statement 1: x is a multiple of y
x = n* y
Now, the question becomes is 10*n*y-1 is divisible by y
Case 1: Answer is yes, if y is 1.
Case 2: Answer is no, if the y is any number other than 1 [ This is true from the theory of Co-primes i.e Two consecutive number are co-prime meaning
donot share any common factor except 1. Same holds true if one is multiple of the other ]
Therefore insufficient

Statement 2: y is a prime number
y can be 2, 3 5, 7 etc
Insufficient

Combining 1 and 2: we can say only the case 2 remains. And therefore using both statements together we can solve the problem. Answer C)
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 6859
Premium Member
Re: If x is a positive integer, is (10x - 1) divisible by y [#permalink]

Show Tags

New post 27 Jan 2018, 02:43
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Re: If x is a positive integer, is (10x - 1) divisible by y   [#permalink] 27 Jan 2018, 02:43
Display posts from previous: Sort by

If x is a positive integer, is (10x - 1) divisible by y

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

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®.