BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

If x/(x+y)=6 then . . .

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Legendary Member
Posts: 2276
Joined: Sat Oct 14, 2017 6:10 am
Followed by:3 members

If x/(x+y)=6 then . . .

by VJesus12 » Tue Oct 31, 2017 10:55 am
$$If\ \frac{x}{x+y}=6\ then\ \frac{y}{y+x}=$$

A -5
B 5/11
C 1
D 11/5
E 5

The OA is A.

How can I find this value without knowing x and y values? Experts, please give me some explanation here.
Top
Source: — Problem Solving |
User avatar
Legendary Member
Posts: 2663
Joined: Wed Jan 14, 2015 8:25 am
Location: Boston, MA
Thanked: 1153 times
Followed by:128 members
GMAT Score:770

by DavidG@VeritasPrep » Tue Oct 31, 2017 11:17 am
VJesus12 wrote:$$If\ \frac{x}{x+y}=6\ then\ \frac{y}{y+x}=$$

A -5
B 5/11
C 1
D 11/5
E 5

The OA is A.

How can I find this value without knowing x and y values? Experts, please give me some explanation here.
You could pick some easy numbers. Say x = 6. Well, if x/(x+y) = 6, and x, the numerator, is 6, then the denominator will have to be 1, so y would have to be - 5, as 6 + (-5) = 1.

Now take our values: x = 6 and y = -5 and plug them into y/(x+y) = -5/(6 + -5) = -5/1 = -5. The answer is A
Veritas Prep | GMAT Instructor

Veritas Prep Reviews
Save $100 off any live Veritas Prep GMAT Course
Top
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

If x/(x+y)=6 then . . .

by GMATGuruNY » Tue Oct 31, 2017 11:38 am
VJesus12 wrote:$$If\ \frac{x}{x+y}=6\ then\ \frac{y}{y+x}=$$

A -5
B 5/11
C 1
D 11/5
E 5

The OA is A.

How can I find this value without knowing x and y values? Experts, please give me some explanation here.
x(x+y) = 6
x = 6(x+y)
x = 6x + 6y
-5x = 6y
x = -(6/5)y.

Let y=5, implying that x = -(6/5)(5) = -6.
In this case:
y/(y+x) = 5/(5 + (-6)) = 5/(-1) = -5.

The correct answer is A.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top
Junior | Next Rank: 30 Posts
Posts: 17
Joined: Tue May 30, 2017 6:47 pm
Thanked: 1 times

by barksdale » Tue Oct 31, 2017 1:51 pm
David and Mitch. Can you guys please use the math input method? It makes it a lot easier for me to follow along with your math steps. I and I'm sure others in the forum would greatly appreciate it. Thanks!!!
Top
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

by GMATGuruNY » Wed Nov 01, 2017 3:27 am
barksdale wrote:David and Mitch. Can you guys please use the math input method? It makes it a lot easier for me to follow along with your math steps. I and I'm sure others in the forum would greatly appreciate it. Thanks!!!
I'm not quite sure what you mean by the math input method.
Here's an approach similar to David's:

Let x=6.
Plugging x=6 into the numerator of x/(x+y) = 6, we get:
6/(x+y) = 6.
The equation above is valid only if x+y = 1.
Plugging x=6 into x+y = 1, we get:
6+y = 1
y = 1-6 = -5.

Question: then y/(y+x)?
Plugging x=6 and y=-5 into y/(y+x), we get:
y/(y+x) = -5/(-5+6) = -5/1 = -5.

The correct answer is A.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 8086
Joined: Sat Apr 25, 2015 10:56 am
Location: Los Angeles, CA
Thanked: 43 times
Followed by:29 members

by Scott@TargetTestPrep » Thu Nov 02, 2017 4:06 pm
VJesus12 wrote:$$If\ \frac{x}{x+y}=6\ then\ \frac{y}{y+x}=$$

A -5
B 5/11
C 1
D 11/5
E 5
Since x/(x + y) = 6, (x + y)/x = 1/6. That is:

x/x + y/x = 1/6

1 + y/x = 1/6

y/x = -5/6

x/y = -6/5

Instead of calculating y/(y + x) directly, let's reciprocate y/(y + x) like we did for x/(x + y). Notice that the reciprocal of y/(y + x) is (y + x)/y.

(y + x)/y = y/y + x/y = 1 + (-6/5) = -1/5

Since (y + x)/y = -1/5, y/(y + x) = 1/(-1/5) = -5.

Answer: A

Scott Woodbury-Stewart
Founder and CEO
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

ImageImage
Top
Junior | Next Rank: 30 Posts
Posts: 17
Joined: Tue May 30, 2017 6:47 pm
Thanked: 1 times

by barksdale » Fri Nov 03, 2017 1:40 pm
Mitch, I mean typing your responses in proper math writing:

$$\frac{x}{\left(x+y\right)}=6$$

Instead of x/(x+y)=6

Just a suggestion. It's so much easier to read.
Top
Post new topic Post Reply
• Page 1 of 1