• examPAL
    Most awarded test prep in the world
    Now free for 30 days

    Available with Beat the GMAT members only code

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

    Available with Beat the GMAT members only code

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

    Available with Beat the GMAT members only code

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

    Available with Beat the GMAT members only code

    MORE DETAILS
    Veritas Prep
  • 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

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

This topic has 4 expert replies and 4 member replies
mitzwillrockgmat Master | Next Rank: 500 Posts Default Avatar
Joined
19 May 2010
Posted:
124 messages
Upvotes:
3
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
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

  • +1 Upvote Post
  • Quote
  • Flag

GMAT/MBA Expert

sanju09 GMAT Instructor
Joined
21 Jan 2009
Posted:
3650 messages
Followed by:
81 members
Upvotes:
267
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

  • +1 Upvote Post
  • Quote
  • Flag
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
Upvotes:
47
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

  • +1 Upvote Post
  • Quote
  • Flag
liferocks Legendary Member Default Avatar
Joined
13 Mar 2010
Posted:
576 messages
Followed by:
1 members
Upvotes:
97
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

  • +1 Upvote Post
  • Quote
  • Flag

GMAT/MBA Expert

sanju09 GMAT Instructor
Joined
21 Jan 2009
Posted:
3650 messages
Followed by:
81 members
Upvotes:
267
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

  • +1 Upvote Post
  • Quote
  • Flag
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
Upvotes:
97
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

  • +1 Upvote Post
  • Quote
  • Flag

GMAT/MBA Expert

sanju09 GMAT Instructor
Joined
21 Jan 2009
Posted:
3650 messages
Followed by:
81 members
Upvotes:
267
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

  • +1 Upvote Post
  • Quote
  • Flag
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
Upvotes:
97
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

  • +1 Upvote Post
  • Quote
  • Flag

GMAT/MBA Expert

sanju09 GMAT Instructor
Joined
21 Jan 2009
Posted:
3650 messages
Followed by:
81 members
Upvotes:
267
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

  • +1 Upvote Post
  • Quote
  • Flag
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 lheiannie07 108 topics
2 Roland2rule 63 topics
3 ardz24 63 topics
4 LUANDATO 50 topics
5 AAPL 42 topics
See More Top Beat The GMAT Members...

Most Active Experts

1 image description GMATGuruNY

The Princeton Review Teacher

152 posts
2 image description Jeff@TargetTestPrep

Target Test Prep

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

EMPOWERgmat

104 posts
4 image description Scott@TargetTestPrep

Target Test Prep

96 posts
5 image description Max@Math Revolution

Math Revolution

87 posts
See More Top Beat The GMAT Experts