• 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
  • Veritas Prep
    Free Veritas GMAT Class
    Experience Lesson 1 Live Free

    Available with Beat the GMAT members only code

    MORE DETAILS
    Veritas Prep
  • PrepScholar GMAT
    5 Day FREE Trial
    Study Smarter, Not Harder

    Available with Beat the GMAT members only code

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

    Available with Beat the GMAT members only code

    MORE DETAILS
    Economist Test Prep
  • EMPOWERgmat Slider
    1 Hour Free
    BEAT THE GMAT EXCLUSIVE

    Available with Beat the GMAT members only code

    MORE DETAILS
    EMPOWERgmat Slider
  • Magoosh
    Magoosh
    Study with Magoosh GMAT prep

    Available with Beat the GMAT members only code

    MORE DETAILS
    Magoosh

If x and y are positive integers and 1 + x + y + xy = 15 ...

This topic has 8 member replies
mitzwillrockgmat Master | Next Rank: 500 Posts Default Avatar
Joined
19 May 2010
Posted:
124 messages
Thanked:
3 times
Test Date:
09/2010
Target GMAT Score:
650+
GMAT Score:
1100

If x and y are positive integers and 1 + x + y + xy = 15 ...

Post Thu May 20, 2010 2:24 am
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    If x and y are positive integers and 1 + x + y + xy = 15, what is the value of x + y?

    A. 3
    B. 5
    C. 6
    D. 8
    E. 9

    Please help explain this futher! I get to this point: (1 + x) (1 + y) =15 but what do i do further to get the answer 6?

    1 + x + y + xy = 15
    1 + x + y(1 + x) =15
    (1+x)(1+ y)=15

    now what?? thank you! Smile

    Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
    liferocks Legendary Member Default Avatar
    Joined
    13 Mar 2010
    Posted:
    576 messages
    Followed by:
    1 members
    Thanked:
    97 times
    Post Thu May 20, 2010 2:32 am
    1 + x + y + xy = 15
    or (1+x)(1+y)=15
    15 can be expressed as multiple of two integers as (1,15)and (3,5)

    if (1+x)(1+y)=1*15..1+x=1 or x=0 and y=14..so x+y=14
    if (1+x)(1+y)=3*5..1+x=3 or x=2 and y=4..so x+y=6

    only C is in ans choice
    ans option C

    _________________
    “If you don't know where you are going, any road will get you there.”
    Lewis Carroll



    Last edited by liferocks on Thu May 20, 2010 2:42 am; edited 1 time in total

    Thanked by: mitzwillrockgmat

    GMAT/MBA Expert

    sanju09 GMAT Instructor
    Joined
    21 Jan 2009
    Posted:
    3650 messages
    Followed by:
    81 members
    Thanked:
    267 times
    GMAT Score:
    760
    Post Thu May 20, 2010 2:37 am
    liferocks wrote:
    1 + x + y + xy = 15
    or (1+x)(1+y)=15
    15 can be expressed as multiple (or the product?) of two integers as (1,15)and (3,5)

    if (1+x)(1+y)=1*15..1+x=1 or x=0 and y=14..so x+y=14.............not applicable
    if (1+x)(1+y)=3*5..1+x=3 or x=2 and y=4..so x+y=6....now edited

    only C is in ans choice
    ans option C
    You need to get rid of this...good to see that you have edited while I was quoting your work, and why did you use the spoiler function above?

    _________________
    The mind is everything. What you think you become. –Lord Buddha



    Sanjeev K Saxena
    Quantitative Instructor
    The Princeton Review - Manya Abroad
    Lucknow-226001

    www.manyagroup.com

    Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.
    liferocks Legendary Member Default Avatar
    Joined
    13 Mar 2010
    Posted:
    576 messages
    Followed by:
    1 members
    Thanked:
    97 times
    Post Thu May 20, 2010 2:42 am
    sanju09 wrote:
    liferocks wrote:
    1 + x + y + xy = 15
    or (1+x)(1+y)=15
    15 can be expressed as multiple (or the product?) of two integers as (1,15)and (3,5)

    if (1+x)(1+y)=1*15..1+x=1 or x=0 and y=14..so x+y=14.............not applicable
    if (1+x)(1+y)=3*5..1+x=3 or x=2 and y=4..so x+y=6....now edited

    only C is in ans choice
    ans option C
    You need to get rid of this...good to see that you have edited while I was quoting your work, and why did you use the spoiler function above?
    Now used the spoiler in both places

    _________________
    “If you don't know where you are going, any road will get you there.”
    Lewis Carroll

    GMAT/MBA Expert

    sanju09 GMAT Instructor
    Joined
    21 Jan 2009
    Posted:
    3650 messages
    Followed by:
    81 members
    Thanked:
    267 times
    GMAT Score:
    760
    Post Thu May 20, 2010 2:48 am
    ...and what should be the correct wordings in this case?

    this: 15 can be expressed as multiple of two integers

    or that: 15 can be expressed as the product of two integers

    multiple and the product are two different words with different meanings in mathematics

    _________________
    The mind is everything. What you think you become. –Lord Buddha



    Sanjeev K Saxena
    Quantitative Instructor
    The Princeton Review - Manya Abroad
    Lucknow-226001

    www.manyagroup.com

    Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.
    liferocks Legendary Member Default Avatar
    Joined
    13 Mar 2010
    Posted:
    576 messages
    Followed by:
    1 members
    Thanked:
    97 times
    Post Thu May 20, 2010 2:51 am
    sanju09 wrote:
    ...and what should be the correct wordings in this case?

    this: 15 can be expressed as multiple of two integers

    or that: 15 can be expressed as the product of two integers
    Hmm..second one is definitely right and conveys the meaning correctly..but technically first one is also correct if we take a multiplicity factor as 1 Very Happy

    _________________
    “If you don't know where you are going, any road will get you there.”
    Lewis Carroll

    GMAT/MBA Expert

    sanju09 GMAT Instructor
    Joined
    21 Jan 2009
    Posted:
    3650 messages
    Followed by:
    81 members
    Thanked:
    267 times
    GMAT Score:
    760
    Post Thu May 20, 2010 2:54 am
    liferocks wrote:
    sanju09 wrote:
    ...and what should be the correct wordings in this case?

    this: 15 can be expressed as multiple of two integers

    or that: 15 can be expressed as the product of two integers
    Hmm..second one is definitely right and conveys the meaning correctly..but technically first one is also correct if we take a multiplicity factor as 1 Very Happy
    postmortem is not carried out on living beings

    _________________
    The mind is everything. What you think you become. –Lord Buddha



    Sanjeev K Saxena
    Quantitative Instructor
    The Princeton Review - Manya Abroad
    Lucknow-226001

    www.manyagroup.com

    Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.
    kstv Legendary Member Default Avatar
    Joined
    15 Jan 2010
    Posted:
    610 messages
    Followed by:
    2 members
    Thanked:
    47 times
    Post Thu May 20, 2010 3:04 am
    if (1+x)(1+y) = 15
    and x any y are +ve integers
    then (1+x) (1+y) = 5*3 and not 15*1
    cos 1+x or 1+y = 1 implies x or y = 0
    if 1+x = 5
    1+y = 3
    it is not necessary to find the values of x and y seperately
    adding the two (1+x)+(1+y) = 8
    x+y = 6

    GMAT/MBA Expert

    sanju09 GMAT Instructor
    Joined
    21 Jan 2009
    Posted:
    3650 messages
    Followed by:
    81 members
    Thanked:
    267 times
    GMAT Score:
    760
    Post Thu May 20, 2010 3:10 am
    kstv wrote:
    if (1+x)(1+y) = 15
    and x any y are +ve integers
    then (1+x) (1+y) = 5*3 and not 15*1
    cos 1+x or 1+y = 1 implies x or y = 0
    if 1+x = 5
    1+y = 3
    it is not necessary to find the values of x and y seperately
    adding the two (1+x)+(1+y) = 8
    x+y = 6
    your name was missing in the hit list of my Quant Commandos

    _________________
    The mind is everything. What you think you become. –Lord Buddha



    Sanjeev K Saxena
    Quantitative Instructor
    The Princeton Review - Manya Abroad
    Lucknow-226001

    www.manyagroup.com

    Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.

    Best Conversation Starters

    1 LUANDATO 138 topics
    2 lheiannie07 91 topics
    3 Roland2rule 79 topics
    4 AAPL 71 topics
    5 swerve 66 topics
    See More Top Beat The GMAT Members...

    Most Active Experts

    1 image description EconomistGMATTutor

    The Economist GMAT Tutor

    160 posts
    2 image description Jay@ManhattanReview

    Manhattan Review

    128 posts
    3 image description GMATGuruNY

    The Princeton Review Teacher

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

    EMPOWERgmat

    118 posts
    5 image description Brent@GMATPrepNow

    GMAT Prep Now Teacher

    114 posts
    See More Top Beat The GMAT Experts