• PrepScholar GMAT
    5 Day FREE Trial
    Study Smarter, Not Harder

    Available with Beat the GMAT members only code

    MORE DETAILS
    PrepScholar GMAT
  • Economist Test Prep
    Free Trial & Practice Exam
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    Economist Test Prep
  • Veritas Prep
    Free Veritas GMAT Class
    Experience Lesson 1 Live Free

    Available with Beat the GMAT members only code

    MORE DETAILS
    Veritas Prep
  • Kaplan Test Prep
    Free Practice Test & Review
    How would you score if you took the GMAT

    Available with Beat the GMAT members only code

    MORE DETAILS
    Kaplan Test Prep
  • e-gmat Exclusive Offer
    Get 300+ Practice Questions
    25 Video lessons and 6 Webinars for FREE

    Available with Beat the GMAT members only code

    MORE DETAILS
    e-gmat Exclusive Offer
  • Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

    MORE DETAILS
    Magoosh
  • Varsity Tutors
    Award-winning private GMAT tutoring
    Register now and save up to $200

    Available with Beat the GMAT members only code

    MORE DETAILS
    Varsity Tutors
  • EMPOWERgmat Slider
    1 Hour Free
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider
  • Target Test Prep
    5-Day Free Trial
    5-day free, full-access trial TTP Quant

    Available with Beat the GMAT members only code

    MORE DETAILS
    Target Test Prep

Kaplan DS

This topic has 2 member replies
gmatme Junior | Next Rank: 30 Posts Default Avatar
Joined
06 Mar 2007
Posted:
18 messages

Kaplan DS

Post Sun Apr 29, 2007 10:02 am
if X^2 + 5Y = 49, is Y an Integer?

1) 1 < X < 4
2) X^2 is an integer.

The answer is E? I think it should be C, can some one explain why E?

The following is my reason for C)

From 1) X could be 2, 3, 3/2 etc. If X is 2 or 3 then Y is an integer but if 3/2 then it is not so, 1) is not sufficient.

From 2) not sufficient

From 1 and 2. X^2 is integer then X should be integer so possible values are 2,3. For these 2 values Y is integer - so sufficient.

  • +1 Upvote Post
  • Quote
  • Flag
Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
bww Senior | Next Rank: 100 Posts Default Avatar
Joined
29 Apr 2007
Posted:
55 messages
Upvotes:
1
Top Reply
Post Mon Apr 30, 2007 7:04 pm
here's how i look at it:

1) X can be any value between 1 and 4, not inclusive. let's assume X=1.1. plugging that into the question stem gives us 1.21+5Y=49. pretty obvious that Y is not an integer. let's say X=2. then we have 4+5Y=49. Y then is an integer. so we have determined both "yes" and "no" to the question. 1) is not sufficient. rule out A and D.

2) cover 1) up momentarily and just consider 2). X^2 is an integer, but X is not necessarily an integer. in the example given by jayhawk2001, the sqrt of 3 is roughly 1.73. point is, unless we know what X is, X^2 can be any integer (1, 5, 85, etc.), which gives us both "yes" and "no" to the question if Y is an integer. thus, 2) is not sufficient, so we rule out B. but 2) also indirectly addresses combining statements 1) and 2). since X^2 is part of the question and we know that X^2 IS an integer, we get different values for Y when X^2 takes on different values. thus, 1) and 2) are both insufficient. the answer is E.

  • +1 Upvote Post
  • Quote
  • Flag
jayhawk2001 Community Manager
Joined
28 Jan 2007
Posted:
789 messages
Followed by:
1 members
Upvotes:
30
Top Reply
Post Sun Apr 29, 2007 1:16 pm
gmatme wrote:
From 1 and 2. X^2 is integer then X should be integer so possible values are 2,3. For these 2 values Y is integer - so sufficient.
If X^2 is an integer, X need not necessarily be an integer. Take X^2 = 3.
X = sqrt(3) [ positive root ] which is not an integer.

Hence E

  • +1 Upvote Post
  • Quote
  • Flag

Best Conversation Starters

1 lheiannie07 116 topics
2 LUANDATO 68 topics
3 swerve 65 topics
4 ardz24 65 topics
5 Roland2rule 64 topics
See More Top Beat The GMAT Members...

Most Active Experts

1 image description Scott@TargetTestPrep

Target Test Prep

198 posts
2 image description Brent@GMATPrepNow

GMAT Prep Now Teacher

181 posts
3 image description Jeff@TargetTestPrep

Target Test Prep

168 posts
4 image description Rich.C@EMPOWERgma...

EMPOWERgmat

134 posts
5 image description GMATGuruNY

The Princeton Review Teacher

119 posts
See More Top Beat The GMAT Experts