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Need Help Solving a problem

This topic has 5 expert replies and 1 member reply
psavalia Newbie | Next Rank: 10 Posts Default Avatar
Joined
14 May 2014
Posted:
2 messages

Need Help Solving a problem

Post Thu May 22, 2014 1:42 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    The following is DS question from Kaplan Premier 2014 on page 699.

    What is the value of integer n?

    (1) n = n^4
    (2) 1^n does not equal 0

    ** Insert Standard DS option choices here**

    I came to the conclusion that the answer is B. Only statement 2 is sufficient. However the book claims its C; Both statements together are sufficient.
    My logic behind this is statement 1 is insufficient because it yields 1 or 0 as possible answers. However in statement 2 only 0 can be the answer thus making it sufficient as 1^0 = 1 and 1 does not equal 0. Whats your take on it guys?
    [/list][/i]

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    Post Thu May 22, 2014 1:51 pm
    psavalia wrote:
    What is the value of integer n?

    (1) n = n^4
    (2) 1^n does not equal 0

    Are you sure you transcribed the question correctly??
    1^n can never equal 0, so statement 2 tells us nothing.

    If you correctly transcribed, then the answer is actually E

    Cheers,
    Brent

    _________________
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    psavalia Newbie | Next Rank: 10 Posts Default Avatar
    Joined
    14 May 2014
    Posted:
    2 messages
    Post Thu May 22, 2014 1:59 pm
    Good catch Brent, you are right I did transcribe it wrong. Statement 2 should read: "1^n does not equal n"

    so...

    (1) n = n^4
    (2) 1^n does not equal n

    Post Thu May 22, 2014 2:13 pm
    psavalia wrote:
    What is the value of integer n?

    (1) n = n^4
    (2) 1^n does not equal n

    Target question: What is the value of integer n?

    Given: n is an integer

    Statement 1: n = n^4
    There are two values of n that satisfy this equation.
    Case a: n = 0
    Case b: n = 1
    Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

    Statement 2: 1^n does not equal n
    There are several values of n that satisfy this condition. Here are three:
    Case a: n = 0
    Case b: n = 2
    Case c: n = 3 etc...[Aside: statement 2 essentially tells us that n ≠ 1]
    Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT


    Statements 1 and 2 combined
    Statement 1 tells us that n = 0 OR n = 1
    Statement 2 tells us that n ≠ 1
    So, it MUST BE THE CASE that n = 0
    Since we can answer the target question with certainty, the combined statements are SUFFICIENT

    Answer = C

    Cheers,
    Brent

    _________________
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    Post Mon May 26, 2014 8:02 am
    psavalia wrote:
    I came to the conclusion that the answer is B. Only statement 2 is sufficient. However the book claims its C; Both statements together are sufficient.
    My logic behind this is statement 1 is insufficient because it yields 1 or 0 as possible answers. However in statement 2 only 0 can be the answer thus making it sufficient as 1^0 = 1 and 1 does not equal 0. Whats your take on it guys?
    [/list][/i]
    It sounds to me like you have fallen prey to STATEMENT CARRYOVER. You were taking the information you had gotten from statement 1 and applying it to statement 2 without evaluating statement 2 by itself.

    In statement 2, 1^n does not equal n could be true for an infinite number of values:
    1^2 does not equal 2.
    1^-5 does not equal 5.
    etc.

    In fact, the only thing that statement 2 tells us is that n is not equal to 1.

    Be very wary of statement carryover - do you often find yourself picking B when the answer should have been C? I will often have my students cross out whatever they wrote down for statement 1 before reading statement 2 to avoid this problem.

    _________________


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    Manhattan Prep GMAT & GRE instructor
    EdM in Mind, Brain, and Education
    Harvard Graduate School of Education


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    Post Mon May 26, 2014 8:03 am
    For more on STATEMENT CARRYOVER, see:
    http://www.beatthegmat.com/gmat-og-13-t241746.html#653748

    _________________


    Ceilidh Erickson
    Manhattan Prep GMAT & GRE instructor
    EdM in Mind, Brain, and Education
    Harvard Graduate School of Education


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    Sign up for a FREE TRIAL, and learn why we have the highest ratings in the GMAT industry!

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    Post Mon May 26, 2014 1:27 pm
    As Ceilidh notes, STATEMENT CARRYOVER is a very common mistake that students make when they begin tackling Data Dufficiency questions.

    This and several other common Data Sufficiency (DS) mistakes are covered in our free videos:
    - Common Data Sufficiency mistakes - part I: http://www.gmatprepnow.com/module/gmat-data-sufficiency?id=1097
    - Common Data Sufficiency mistakes - part II: http://www.gmatprepnow.com/module/gmat-data-sufficiency?id=1105

    Cheers,
    Brent

    _________________
    Brent Hanneson – Founder of GMATPrepNow.com
    Use our video course along with Beat The GMAT's free 60-Day Study Guide

    Check out the online reviews of our course

    GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months!

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