BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

Divisibility and Primes!

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members
Location: Milpitas, CA
Thanked: 1854 times
GMAT Score:770

by Anurag@Gurome » Thu Oct 27, 2011 10:06 am
Ahmed MS wrote:Q: When 15 is divided by Y, the remainder is Y - 3. If Y must be an integer, what are all the possible values of Y?
--> 15 = ky + (y - 3)
--> 15 + 3 = ky + y
--> (k + 1)y = 18

Hence, y must be a factor of 18 but not of 15.
Hence, possible values of y are 2, 6, 9, and 18.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 150
Joined: Thu May 05, 2011 10:04 amFollowed by: 4 members
Thanked: 5 times

by thestartupguy » Fri Oct 28, 2011 5:44 am
Anurag@Gurome wrote:
Ahmed MS wrote:Q: When 15 is divided by Y, the remainder is Y - 3. If Y must be an integer, what are all the possible values of Y?
--> 15 = ky + (y - 3)
--> 15 + 3 = ky + y
--> (k + 1)y = 18

Hence, y must be a factor of 18 but not of 15.
Hence, possible values of y are 2, 6, 9, and 18.
Anurag,

Is y=2 a correct solution coz. 15 mod 2 = 1 (and not 3)?

Please correct if my understanding is wrong
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members
Location: Milpitas, CA
Thanked: 1854 times
GMAT Score:770

by Anurag@Gurome » Fri Oct 28, 2011 7:20 am
msr4mba wrote:...Is y=2 a correct solution coz. 15 mod 2 = 1 (and not 3)?
From mathematical point of view, there is no reason to discard 2 as the value of y.

If a and d are integers, with d non-zero, then a remainder is an integer r such that a = qd + r for some integer q, and with 0 ≤ |r| < |d|. Hence, the remainder can be either positive or negative. Generally we deal with positive reminders.

For example, when 15 is divided by 4, generally we say the remainder is 3 because 15 = 3*4 + 3. But 15 can also be written as 4*4 - 1, in which case -1 is the remainder.

Similarly, here for y = 2, when 15 is divided by y, the remainder is (y - 3) = (2 - 3) = -1 which is the case when 15 = 8*2 - 1

Hope that helps.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 10
Joined: Sun Jul 24, 2011 10:24 pm

by amit.lohchab » Sat Oct 29, 2011 6:20 am
Hi Anurag,

Since in the question it is not stated that remainder is a non-zero integer so 3 can be a possible value of Y. please explain.

Thanks,
Amit
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1