It is currently 21 Oct 2017, 16:27

Close

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If x/(x+y) = n, and x/(x-y) = m, then x/y = ? (|x| does not

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Intern
Intern
avatar
Joined: 21 Nov 2013
Posts: 12

Kudos [?]: 22 [0], given: 9

If x/(x+y) = n, and x/(x-y) = m, then x/y = ? (|x| does not [#permalink]

Show Tags

New post 19 Feb 2014, 22:05
14
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

67% (02:37) correct 33% (02:43) wrong based on 202 sessions

HideShow timer Statistics

If x/(x+y) = n, and x/(x-y) = m, then x/y = ? (|x| does not equal |y|, xy does not equal 0)

A. 3mn/2
B. (3m)/(2n)
C. (n * (m+2))/2
D. 2nm / (m-n)
E. (n^2 - m^2) / nm
[Reveal] Spoiler: OA

_________________

Any and all kudos are greatly appreciated. Thank you.

Kudos [?]: 22 [0], given: 9

Expert Post
2 KUDOS received
Veritas Prep GMAT Instructor
User avatar
G
Joined: 16 Oct 2010
Posts: 7676

Kudos [?]: 17381 [2], given: 232

Location: Pune, India
Re: If x/(x+y) = n, and x/(x-y) = m, then x/y = ? (|x| does not [#permalink]

Show Tags

New post 19 Feb 2014, 22:36
2
This post received
KUDOS
Expert's post
2
This post was
BOOKMARKED
MrWallSt wrote:
If x / (x+y) = n, and x / (x-y) = m, then x/y=? (|x| does not equal |y|, xy does not equal 0)

A. 3mn/2
B. (3m)/(2n)
C. (n * (m+2))/2
D. 2nm / (m-n)
E. (n^2 - m^2) / nm


You can do it either algebraically or by assuming numbers:

Algebra:
Note that we are happier with (x+y)/x rather than x/(x+y) since in the former case we can make manipulations easily. So let's take the inverse of both n and m

\(\frac{1}{n} = \frac{(x+y)}{x} = 1 + \frac{y}{x}\) ....(I)
\(\frac{1}{m} = \frac{(x-y)}{x} = 1 - \frac{y}{x}\) .....(II)

Since we have both m and n in our answer, lets subtract II from I to get

\(\frac{1}{n} - \frac{1}{m} = \frac{2y}{x}\)

\(\frac{(m-n)}{2mn} = \frac{y}{x}\)

\(\frac{x}{y} = \frac{2mn}{(m-n)}\)

Answer (D)

Or Plug in numbers: x = 2, y = 1
n = x/(x+y) = 2/3
m = x/(x-y) = 2

x/y = 2

Now put n = 2/3 and m = 2 in the options. Only option (D) gives you x/y = 2.

Hence answer (D)
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199

Veritas Prep Reviews

Kudos [?]: 17381 [2], given: 232

Intern
Intern
avatar
Joined: 21 Nov 2013
Posts: 12

Kudos [?]: 22 [0], given: 9

Re: If x/(x+y) = n, and x/(x-y) = m, then x/y = ? (|x| does not [#permalink]

Show Tags

New post 19 Feb 2014, 22:59
@Karishma thanks for the post. Your blogs are extremely helpful btw. I am not sure if you ever followed up about your CFA, but I hope that went well for you.
_________________

Any and all kudos are greatly appreciated. Thank you.

Kudos [?]: 22 [0], given: 9

1 KUDOS received
Director
Director
User avatar
S
Affiliations: CrackVerbal
Joined: 03 Oct 2013
Posts: 512

Kudos [?]: 574 [1], given: 6

Location: India
GMAT 1: 780 Q51 V46
Re: If x/(x+y) = n, and x/(x-y) = m, then x/y = ? (|x| does not [#permalink]

Show Tags

New post 19 Feb 2014, 23:32
1
This post received
KUDOS
1
This post was
BOOKMARKED
MrWallSt wrote:
If x / (x+y) = n, and x / (x-y) = m, then x/y=? (|x| does not equal |y|, xy does not equal 0)

A. 3mn/2
B. (3m)/(2n)
C. (n * (m+2))/2
D. 2nm / (m-n)
E. (n^2 - m^2) / nm


Let us say x = 3, y = 1, n = 0.75, m = 1.5

x/y = 3

(A) 3(3/2)(3/4) = 9/8 (Eliminated)
(B) 3(3/2) 2(3/4) = (Eliminated)
(C) (3/4) (3/2 + 2)/2 = (Eliminated)
(D) 2(3/4)(3/2)/(.75) = 3 (BINGO!)
(E) Eliminated

Hence answer is D
_________________

Enroll for our GMAT Trial Course here -
http://gmatonline.crackverbal.com/

Learn all PS and DS strategies here-
http://gmatonline.crackverbal.com/p/mastering-quant-on-gmat

For more info on GMAT and MBA, follow us on @AskCrackVerbal

Kudos [?]: 574 [1], given: 6

Current Student
avatar
Joined: 01 Aug 2014
Posts: 41

Kudos [?]: 15 [0], given: 46

Location: India
GPA: 3.65
GMAT ToolKit User
Re: If x/(x+y) = n, and x/(x-y) = m, then x/y = ? (|x| does not [#permalink]

Show Tags

New post 24 May 2015, 22:24
CrackVerbalGMAT wrote:
MrWallSt wrote:
If x / (x+y) = n, and x / (x-y) = m, then x/y=? (|x| does not equal |y|, xy does not equal 0)

A. 3mn/2
B. (3m)/(2n)
C. (n * (m+2))/2
D. 2nm / (m-n)
E. (n^2 - m^2) / nm


Let us say x = 3, y = 1, n = 0.75, m = 1.5

x/y = 3

(A) 3(3/2)(3/4) = 9/8 (Eliminated)
(B) 3(3/2) 2(3/4) = (Eliminated)
(C) (3/4) (3/2 + 2)/2 = (Eliminated)
(D) 2(3/4)(3/2)/(.75) = 3 (BINGO!)
(E) Eliminated

Hence answer is D


Sorry for opening a long answered question.

with algebric solution, i am getting many answers in terms of m & n. so the problem needed to be solved by picking numbers.
when we pick x = 3 & y = 1. I am getting B & D both as answer and but with x = 2 & y= 3. I am getting D as an answer. shouldnt it be unique for all numbers, since there is no restriction (like x, y = consequetive or x>y or viceversa) on picking numbers.

Kudos [?]: 15 [0], given: 46

Expert Post
Veritas Prep GMAT Instructor
User avatar
G
Joined: 16 Oct 2010
Posts: 7676

Kudos [?]: 17381 [0], given: 232

Location: Pune, India
Re: If x/(x+y) = n, and x/(x-y) = m, then x/y = ? (|x| does not [#permalink]

Show Tags

New post 24 May 2015, 22:53
Alaukik wrote:
CrackVerbalGMAT wrote:
MrWallSt wrote:
If x / (x+y) = n, and x / (x-y) = m, then x/y=? (|x| does not equal |y|, xy does not equal 0)

A. 3mn/2
B. (3m)/(2n)
C. (n * (m+2))/2
D. 2nm / (m-n)
E. (n^2 - m^2) / nm


Let us say x = 3, y = 1, n = 0.75, m = 1.5

x/y = 3

(A) 3(3/2)(3/4) = 9/8 (Eliminated)
(B) 3(3/2) 2(3/4) = (Eliminated)
(C) (3/4) (3/2 + 2)/2 = (Eliminated)
(D) 2(3/4)(3/2)/(.75) = 3 (BINGO!)
(E) Eliminated

Hence answer is D


Sorry for opening a long answered question.

with algebric solution, i am getting many answers in terms of m & n. so the problem needed to be solved by picking numbers.
when we pick x = 3 & y = 1. I am getting B & D both as answer and but with x = 2 & y= 3. I am getting D as an answer. shouldnt it be unique for all numbers, since there is no restriction (like x, y = consequetive or x>y or viceversa) on picking numbers.


When you take one of the numbers as 1 or 0, or when you take numbers to be equal, you could get multiple options satisfying your conditions.

For example, if n = 1
3n/(m+n) will give the same result as 3/(m+n).

Sometimes, you will get the same answer from multiple options if the options are written intelligently. So you could need to try out 2 or even 3 sets of values.
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199

Veritas Prep Reviews

Kudos [?]: 17381 [0], given: 232

Current Student
avatar
Joined: 01 Aug 2014
Posts: 41

Kudos [?]: 15 [0], given: 46

Location: India
GPA: 3.65
GMAT ToolKit User
Re: If x/(x+y) = n, and x/(x-y) = m, then x/y = ? (|x| does not [#permalink]

Show Tags

New post 25 May 2015, 04:57
VeritasPrepKarishma wrote:
When you take one of the numbers as 1 or 0, or when you take numbers to be equal, you could get multiple options satisfying your conditions.

For example, if n = 1
3n/(m+n) will give the same result as 3/(m+n).

Sometimes, you will get the same answer from multiple options if the options are written intelligently. So you could need to try out 2 or even 3 sets of values.


well the question states xy != 0, so x or y cant be 0. also |x| != |y| so they cant be equal either.

I was hoping for a more bullet proof solution for this question. as 2 sets will take more time. we will get answer but at a huge expense of time.

Kudos [?]: 15 [0], given: 46

Expert Post
Veritas Prep GMAT Instructor
User avatar
G
Joined: 16 Oct 2010
Posts: 7676

Kudos [?]: 17381 [0], given: 232

Location: Pune, India
Re: If x/(x+y) = n, and x/(x-y) = m, then x/y = ? (|x| does not [#permalink]

Show Tags

New post 25 May 2015, 20:25
Alaukik wrote:
VeritasPrepKarishma wrote:
When you take one of the numbers as 1 or 0, or when you take numbers to be equal, you could get multiple options satisfying your conditions.

For example, if n = 1
3n/(m+n) will give the same result as 3/(m+n).

Sometimes, you will get the same answer from multiple options if the options are written intelligently. So you could need to try out 2 or even 3 sets of values.


well the question states xy != 0, so x or y cant be 0. also |x| != |y| so they cant be equal either.

I was hoping for a more bullet proof solution for this question. as 2 sets will take more time. we will get answer but at a huge expense of time.


Note that it is a generic comment about number plugging - not just specific to this question.

Also, I have given the algebra solution above - as "bulletproof" as you can get.
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199

Veritas Prep Reviews

Kudos [?]: 17381 [0], given: 232

1 KUDOS received
Manager
Manager
User avatar
Joined: 11 Nov 2011
Posts: 74

Kudos [?]: 11 [1], given: 96

Location: United States
Concentration: Finance, Human Resources
GPA: 3.33
WE: Consulting (Non-Profit and Government)
GMAT ToolKit User
Re: If x/(x+y) = n, and x/(x-y) = m, then x/y = ? (|x| does not [#permalink]

Show Tags

New post 02 Aug 2015, 06:55
1
This post received
KUDOS
VeritasPrepKarishma your solution is excellence. I am wondering, how do we know that one form of fraction (you mentioned it as case) is easier to manipulate than another? I tried to solve this problem using the original form of fraction but I ended up nowhere. Do you have the solution using original form of the fraction?

Kudos [?]: 11 [1], given: 96

Expert Post
2 KUDOS received
Veritas Prep GMAT Instructor
User avatar
G
Joined: 16 Oct 2010
Posts: 7676

Kudos [?]: 17381 [2], given: 232

Location: Pune, India
Re: If x/(x+y) = n, and x/(x-y) = m, then x/y = ? (|x| does not [#permalink]

Show Tags

New post 02 Aug 2015, 23:30
2
This post received
KUDOS
Expert's post
evdo wrote:
VeritasPrepKarishma your solution is excellence. I am wondering, how do we know that one form of fraction (you mentioned it as case) is easier to manipulate than another? I tried to solve this problem using the original form of fraction but I ended up nowhere. Do you have the solution using original form of the fraction?


When you need to separate the variables, multiple terms in the numerator are easy to handle since you can split them:

(x+y)/ x = x/x + y/x = 1 + y/x

But if they are in the denominator, you cannot separate them.

You can start with the equations as they are but you will eventually cross multiply to simplify the denominator. If you do different things with the equations, you will get different but equivalent expressions. So a case can be made to do the question by number plugging instead.
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199

Veritas Prep Reviews

Kudos [?]: 17381 [2], given: 232

GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 16587

Kudos [?]: 273 [0], given: 0

Premium Member
Re: If x/(x+y) = n, and x/(x-y) = m, then x/y = ? (|x| does not [#permalink]

Show Tags

New post 04 Oct 2017, 11:56
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Kudos [?]: 273 [0], given: 0

Re: If x/(x+y) = n, and x/(x-y) = m, then x/y = ? (|x| does not   [#permalink] 04 Oct 2017, 11:56
Display posts from previous: Sort by

If x/(x+y) = n, and x/(x-y) = m, then x/y = ? (|x| does not

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.