• Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

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

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider
  • 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
  • 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
  • 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

lost in the sauce

This topic has 2 expert replies and 1 member reply
MalcolmW Junior | Next Rank: 30 Posts Default Avatar
Joined
01 Nov 2015
Posted:
20 messages

lost in the sauce

Post Thu Nov 19, 2015 6:47 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    If A and B are positive integers, is the product AB even?
    (1) The sum A + B is odd.
    (2) A is even.

    Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!

    Top Member

    Post Thu Nov 19, 2015 7:17 pm
    What a cool little question.

    Statement 1 tells us that the sum of the two integers is odd.

    If we add two odd integers, we get an even integer. 3 + 5 = 8

    If we add two even integers, we get an even integer. 2 + 166 = 168

    The only way to get an odd integer by adding two integers is by having one of them be odd and the other even. 5 + 8 = 13

    So either A or B has to be even and so the product AB must be even, and Statement 1 is sufficient.

    Statement 2 tells us that A is even, and so the product AB must be even, and Statement 2 is sufficient.

    Choose D.

    _________________
    Marty Murray
    GMAT Coach
    m.w.murray@hotmail.com
    http://infinitemindprep.com/
    In Person in the New York Area and Online Worldwide

    Post Fri Nov 20, 2015 7:13 am
    For this question, you need to know the following:

    1. ODD +/- ODD = EVEN
    2. ODD +/- EVEN = ODD
    3. EVEN +/- EVEN = EVEN

    4. (ODD)(ODD) = ODD
    5. (ODD)(EVEN) = EVEN
    6. (EVEN)(EVEN) = EVEN


    For more on ODD and EVEN integers, watch our free video - http://www.gmatprepnow.com/module/gmat-integer-properties/video/837

    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
    Come see all of our free resources

    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!

    GMAT/MBA Expert

    Max@Math Revolution Legendary Member
    Joined
    24 Jul 2015
    Posted:
    846 messages
    Followed by:
    22 members
    Thanked:
    19 times
    GMAT Score:
    Post Sun Nov 22, 2015 1:06 am
    Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

    If A and B are positive integers, is the product AB even?
    (1) The sum A + B is odd.
    (2) A is even.

    There are 2 variables (A,B), but only 2 equations are given by the conditions, so there is high chance (C) will be our answer.
    Looking at the conditions together, A=even, B=odd, so it is a 'yes' and the condition is sufficient, making the answer seem like (C), but this is a commonly made mistake;
    if we look at them separately,
    For condition 1, A+B=odd --> (A,B)=(odd,even),(even,odd). The answer always becomes 'yes' and the condition is sufficient.
    For condition 2, in A=even --> AB=even*B=even, the answer becomes 'yes' and the condition is sufficient as well. The answer is (D).

    For cases where we need 2 more equations, such as original conditions with “2 variables”, or “3 variables and 1 equation”, or “4 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 70% chance that C is the answer, while E has 25% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since C is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, D or E.

    _________________

    Math Revolution
    Finish GMAT Quant Section with 10 minutes to spare.
    The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
    Get extra 10% discount for our members
    Unlimited Access to over 120 free video lessons - try it yourself
    See our Youtube demo
    Email to : info@mathrevolution.com

    Best Conversation Starters

    1 lheiannie07 116 topics
    2 ardz24 64 topics
    3 swerve 63 topics
    4 LUANDATO 62 topics
    5 M7MBA 57 topics
    See More Top Beat The GMAT Members...

    Most Active Experts

    1 image description Brent@GMATPrepNow

    GMAT Prep Now Teacher

    170 posts
    2 image description EconomistGMATTutor

    The Economist GMAT Tutor

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

    EMPOWERgmat

    122 posts
    4 image description GMATGuruNY

    The Princeton Review Teacher

    121 posts
    5 image description Scott@TargetTestPrep

    Target Test Prep

    118 posts
    See More Top Beat The GMAT Experts