Live GMAT classes with Target Test Prep start Nov 21 and Nov 22. First class free.

See classes
Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

Newsweek Readers’ Choice Awards 2026 winner: Target Test Prep, #1 Test Prep

Target Test Prep was voted #1 Best Test Prep in the 2026 Newsweek Readers’ Choice™ Awards.

★★★★★5.0563 reviews
GMATLiveTeachStarts Nov 22
Josh Braslow, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Josh Braslow, 20+ years in test prep

Nov 22 · Josh Braslow
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemandStart anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

EXECUTIVE ASSESSMENT

with

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget Test Prep
GMATOnDemandStart anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 563 reviewsTarget Test Prep

Number theory

Expert replies
Post new topic Post Reply
Subscribe topic
Previous Topic Next Topic
Junior | Next Rank: 30 Posts
Posts: 11
Joined: Tue Aug 10, 2010 8:26 am
Thanked: 1 times
by harpritsn » Fri Aug 24, 2012 6:14 am
If (x + y) / (x-y) = 3 and x and y are integers, then which one of the following must be true?

(A) x is divisible by 4
(B) y is an odd number
(C) y is an even integer
(D) x is an even number
(E) x is an irreducible fraction
Top
Join the discussion
Source: — Problem Solving |
Senior | Next Rank: 100 Posts
Posts: 63
Joined: Tue Apr 06, 2010 10:01 pmFollowed by: 1 member
Thanked: 4 times

by prat_agl » Fri Aug 24, 2012 7:22 am
The equation will become --
x+y = 3x-3y
or 2y = x

Now check the answers.

A) not necessary. If Y = 1 x is not divisible by 4.
B) Not necessary. Y can be odd or even.
C) Not necessary. Y can be odd as well.
D) Not necessary. if Y is -ve, then X is also -ve number.
E) Since Y is an integer, X is 2Y which will be an integer. correct answer.
Top
Join the discussion
User avatar
Legendary Member
Posts: 502
Joined: Tue Jun 03, 2008 11:36 pmFollowed by: 21 members
Thanked: 99 times

by vk_vinayak » Fri Aug 24, 2012 7:58 am
Solving the equation we get x=2y. Since it is given that both x and y are integers, x MUST be even.

Ans is D.
- VK

I will (Learn. Recognize. Apply)
Top
Join the discussion
User avatar
Legendary Member
Posts: 502
Joined: Tue Jun 03, 2008 11:36 pmFollowed by: 21 members
Thanked: 99 times

by vk_vinayak » Fri Aug 24, 2012 8:02 am
prat_agl wrote:The equation will become --
x+y = 3x-3y
or 2y = x

Now check the answers.

A) not necessary. If Y = 1 x is not divisible by 4.
B) Not necessary. Y can be odd or even.
C) Not necessary. Y can be odd as well.
D) Not necessary. if Y is -ve, then X is also -ve number.
E) Since Y is an integer, X is 2Y which will be an integer. correct answer.
Negative integers CAN be even (as long as they are multiple of 2). Since it is given that x is an integer, we can discard E, which says x is some sort of fraction.
- VK

I will (Learn. Recognize. Apply)
Top
Join the discussion

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 2623
Joined: Mon Jun 02, 2008 3:17 amFollowed by: 355 members
Location: Montreal
Thanked: 1090 times
GMAT Score:780

by Ian Stewart » Fri Aug 24, 2012 3:18 pm
vk_vinayak wrote:
Since it is given that x is an integer, we can discard E, which says x is some sort of fraction.
You can write integers as fractions if you like. The integer 2 can be written as the "irreducible fraction" 2/1, for example, or as the reducible fraction 6/3.

And that's why answer choice E here doesn't make any mathematical sense, since no matter what x is, it can be written as a fraction, and it can be written as a non-fraction (as a decimal, say). So while it certainly must be true in this question that x is even, and D must be true, it really isn't possible to say one way or the other about E, because it's not at all clear what answer choice E is even supposed to mean. I'm not sure where this question is from, but it's certainly not a real GMAT question.
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

ianstewartgmat.com
Top
Join the discussion
Junior | Next Rank: 30 Posts
Posts: 24
Joined: Sun Aug 12, 2012 9:30 pmFollowed by: 1 member
Thanked: 2 times

by subhash.sonu39 » Fri Aug 24, 2012 11:20 pm
vk_vinayak wrote:Solving the equation we get x=2y. Since it is given that both x and y are integers, x MUST be even.

Ans is D.
I think you are right, D will be a right answer because of this equation 2y = x.
properties of real numbers
Top
Join the discussion
Senior | Next Rank: 100 Posts
Posts: 63
Joined: Tue Apr 06, 2010 10:01 pmFollowed by: 1 member
Thanked: 4 times

by prat_agl » Fri Aug 24, 2012 11:33 pm
if y is -1 then x is -2.
Can we consider a -ve number as even or odd?
Top
Join the discussion
User avatar
Legendary Member
Posts: 502
Joined: Tue Jun 03, 2008 11:36 pmFollowed by: 21 members
Thanked: 99 times

by vk_vinayak » Sat Aug 25, 2012 2:38 am
prat_agl wrote:if y is -1 then x is -2.
Can we consider a -ve number as even or odd?
Yes. Negative integers can be either EVEN or ODD.
Eg: -1, -3, -17, 1, 3, 17 => ODD.
-2, -8, 10, 44, 98 => EVEN
- VK

I will (Learn. Recognize. Apply)
Top
Join the discussion