• Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

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

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider
  • PrepScholar GMAT
    5 Day FREE Trial
    Study Smarter, Not Harder

    Available with Beat the GMAT members only code

    MORE DETAILS
    PrepScholar GMAT
  • 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
  • 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
  • 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

DS - Is n an integer ?

This topic has 8 member replies
II Master | Next Rank: 500 Posts
Joined
10 Dec 2007
Posted:
400 messages
Thanked:
19 times
Target GMAT Score:
700
GMAT Score:
680

DS - Is n an integer ?

Post Sun Aug 10, 2008 2:58 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    Is n an integer ?

    (1) n is an integer

    (2) √n is an integer

    I am interested in learning different approaches in solving this particular question. Thanks.

    Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
    raunekk Legendary Member Default Avatar
    Joined
    16 Apr 2008
    Posted:
    1161 messages
    Thanked:
    56 times
    Target GMAT Score:
    750+
    Post Sun Aug 10, 2008 3:24 pm
    can it be done other then pluggin numbers?

    N^2=2 , then N is not an integer.
    N^2=4 , N is an integer.
    1- insuff

    Sq root N is an integer.

    Then N definately will be an integer.

    2-suff

    Hence,B

    Post Sun Aug 10, 2008 3:41 pm
    1) is insufficient it's ok

    2)
    sqrt(n) is an integer
    The possible values of n so as sqrt(n) is an integer are 1 4 9 16 25 36 ...
    n has to be the square of a number so n has to ba an integer

    Hope it helps

    II Master | Next Rank: 500 Posts
    Joined
    10 Dec 2007
    Posted:
    400 messages
    Thanked:
    19 times
    Target GMAT Score:
    700
    GMAT Score:
    680
    Post Mon Aug 11, 2008 12:32 am
    Guys ... I suppose I am looking for a more thoery based answer to this, rather than just plugging in numbers ...

    Post Mon Aug 11, 2008 3:02 am
    Between plugging in and theory, I would opt for plugging in most of the time...

    For the 1)
    n^2 is an integer --> counter-example with n=sqrt(2)

    For the 2)
    sqrt(n) is an integer --> The form of "n" is: n=a^2 with "a" an integer --> The square of an integer is an integer --> n is an integer

    II Master | Next Rank: 500 Posts
    Joined
    10 Dec 2007
    Posted:
    400 messages
    Thanked:
    19 times
    Target GMAT Score:
    700
    GMAT Score:
    680
    Post Mon Aug 11, 2008 1:36 pm
    pepeprepa wrote:
    Between plugging in and theory, I would opt for plugging in most of the time...

    For the 1)
    n^2 is an integer --> counter-example with n=sqrt(2)

    For the 2)
    sqrt(n) is an integer --> The form of "n" is: n=a^2 with "a" an integer --> The square of an integer is an integer --> n is an integer
    Thanks pepeprepa ... I agree that in a lot of the cases plugging numbers is more efficient, but I want to make sure I understand the theory behind these things !

    cholloway Junior | Next Rank: 30 Posts Default Avatar
    Joined
    30 Mar 2009
    Posted:
    13 messages
    Thanked:
    1 times
    Post Mon Jul 13, 2009 4:37 pm
    I seem to be missing something. What number can you square to get two? Wouldn't that just be an approximation?

    shibal Master | Next Rank: 500 Posts Default Avatar
    Joined
    18 Mar 2009
    Posted:
    345 messages
    Thanked:
    12 times
    Test Date:
    July XX
    Target GMAT Score:
    680+
    GMAT Score:
    660
    Post Mon Jul 13, 2009 5:05 pm
    cholloway wrote:
    I seem to be missing something. What number can you square to get two? Wouldn't that just be an approximation?
    1,4142135623731

    cholloway Junior | Next Rank: 30 Posts Default Avatar
    Joined
    30 Mar 2009
    Posted:
    13 messages
    Thanked:
    1 times
    Post Mon Jul 13, 2009 5:09 pm
    From Wikipideia - The square root of 2, also known as Pythagoras' constant, is the positive real number that, when multiplied by itself, gives the number 2.

    Geometrically the square root of 2 is the length of a diagonal across a square with sides of one unit of length; this follows from the Pythagorean theorem. It was probably the first number known to be irrational. Its numerical value truncated to 65 decimal places[1] is:

    1.41421 35623 73095 04880 16887 24209 69807 85696 71875 37694 80731 76679 73799....


    I thought gmat only deals with rational numbers?

    Best Conversation Starters

    1 lheiannie07 111 topics
    2 ardz24 64 topics
    3 LUANDATO 62 topics
    4 swerve 60 topics
    5 AAPL 57 topics
    See More Top Beat The GMAT Members...

    Most Active Experts

    1 image description Brent@GMATPrepNow

    GMAT Prep Now Teacher

    160 posts
    2 image description EconomistGMATTutor

    The Economist GMAT Tutor

    130 posts
    3 image description Rich.C@EMPOWERgma...

    EMPOWERgmat

    122 posts
    4 image description GMATGuruNY

    The Princeton Review Teacher

    122 posts
    5 image description Scott@TargetTestPrep

    Target Test Prep

    118 posts
    See More Top Beat The GMAT Experts