GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 14 Oct 2019, 11:54

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

If f(x) = (x+1)/(x-1), then the ratio of x to f(y)

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

Hide Tags

Find Similar Topics 
Current Student
avatar
V
Joined: 28 May 2014
Posts: 515
GMAT 1: 730 Q49 V41
GMAT ToolKit User
If f(x) = (x+1)/(x-1), then the ratio of x to f(y)  [#permalink]

Show Tags

New post 24 Feb 2017, 03:05
2
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

77% (02:01) correct 23% (01:39) wrong based on 105 sessions

HideShow timer Statistics

If f(x) = (x+1)/(x-1), then the ratio of x to f(y) where y = f(x) is:

(A) x : y
(B) x^2 : y^2
(C) 1 : 1
(D) y : x
(E) x^2 : y

_________________
Intern
Intern
avatar
Joined: 21 Feb 2017
Posts: 1
Re: If f(x) = (x+1)/(x-1), then the ratio of x to f(y)  [#permalink]

Show Tags

New post 24 Feb 2017, 03:18
C
1:1 is the correct answer, if you expand y = f(x) it results in y=x.
Manager
Manager
avatar
S
Joined: 17 Aug 2012
Posts: 122
Location: India
Concentration: General Management, Strategy
Schools: Copenhagen, ESMT"19
GPA: 3.75
WE: Consulting (Energy and Utilities)
GMAT ToolKit User
Re: If f(x) = (x+1)/(x-1), then the ratio of x to f(y)  [#permalink]

Show Tags

New post 24 Feb 2017, 21:38
replace x in f(x)=(x+1)/ (x-1) with (x+1)/(x-1) and solving -> f(y)= x

x/f(y)=1
answer C
Intern
Intern
avatar
Joined: 20 Feb 2017
Posts: 2
Re: If f(x) = (x+1)/(x-1), then the ratio of x to f(y)  [#permalink]

Show Tags

New post 24 Feb 2017, 23:22
1
I get putting in f(x) for x in to the equation for f(y). This results in:

f(y) = [((x + 1) / (x-1)) + 1] / [((x+1) / (x-1))-1]

can someone illustrate the simplification steps to get to f(y) = x ? It's not apparent to me from these explanations.
Manager
Manager
avatar
D
Joined: 17 May 2015
Posts: 247
Re: If f(x) = (x+1)/(x-1), then the ratio of x to f(y)  [#permalink]

Show Tags

New post 25 Feb 2017, 00:16
1
jjamieson42 wrote:
I get putting in f(x) for x in to the equation for f(y). This results in:

f(y) = [((x + 1) / (x-1)) + 1] / [((x+1) / (x-1))-1]

can someone illustrate the simplification steps to get to f(y) = x ? It's not apparent to me from these explanations.


Hi jjamieson42

Let me try to explain.
Given \(f(x) = \frac{x+1}{x-1}, x \neq 1\) and \(y = f(x)\)

\(f(y) =\frac{ \frac{x+1}{x-1} + 1}{\frac{x+1}{x-1} - 1} = \frac{\frac{x + 1 + x - 1}{x-1}}{\frac{x+1 - x + 1}{x-1}} = \frac{2x}{2} = x\)

Hope it helps.

We can solve this question by plug in the value.
Take x =2 , \(y = f(x) = \frac{2+1}{2-1} = 3\)

\(f(y) = f(3) = \frac{3+1}{3-1} = 2 = x\) => x=f(y) => x:f(y) = 1:1 . Answer (C).

Thanks.
Target Test Prep Representative
User avatar
D
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 8043
Location: United States (CA)
Re: If f(x) = (x+1)/(x-1), then the ratio of x to f(y)  [#permalink]

Show Tags

New post 27 Feb 2017, 12:00
saswata4s wrote:
If f(x) = (x+1)/(x-1), then the ratio of x to f(y) where y = f(x) is:

(A) x : y
(B) x^2 : y^2
(C) 1 : 1
(D) y : x
(E) x^2 : y


We can let x = 2; thus f(2) = (2 + 1)/(2 - 1) = 3/1 = 3.

Since y = f(2), y = 3.

Thus f(y) = f(3) = (3 + 1)/(3 - 1) = 4/2 = 2.

So, the ratio of x to f(y) is 2 : 2, or 1 : 1.

Answer: C
_________________

Scott Woodbury-Stewart

Founder and CEO

Scott@TargetTestPrep.com
TTP - Target Test Prep Logo
122 Reviews

5-star rated online GMAT quant
self study course

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

If you find one of my posts helpful, please take a moment to click on the "Kudos" button.

Intern
Intern
avatar
B
Joined: 26 Apr 2017
Posts: 9
Re: If f(x) = (x+1)/(x-1), then the ratio of x to f(y)  [#permalink]

Show Tags

New post 27 Oct 2018, 11:45
Simply solve

f(y)=x+1x−1+1x+1x−1−1=x+1+x−1x−1x+1−x+1x−1=2x2=x

:)
Intern
Intern
User avatar
S
Joined: 05 Jan 2017
Posts: 35
GMAT ToolKit User
Re: If f(x) = (x+1)/(x-1), then the ratio of x to f(y)  [#permalink]

Show Tags

New post 27 Oct 2018, 12:27
need to find x/ f(f(x))

on solving f(y)= (y+1)/(y-1)
replacing y with f(x)
[(x+1/x-1)+1]/[(x+1/x-1)-1] = x

so x/x -
1/1 = (C)
_________________
----------------------------
Kudos if my post helps!
GMAT Club Bot
Re: If f(x) = (x+1)/(x-1), then the ratio of x to f(y)   [#permalink] 27 Oct 2018, 12:27
Display posts from previous: Sort by

If f(x) = (x+1)/(x-1), then the ratio of x to f(y)

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





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