Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 59628

The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
Updated on: 22 Jun 2018, 01:29
Question Stats:
86% (01:12) correct 14% (01:43) wrong based on 1262 sessions
HideShow timer Statistics
The function f is defined by \(f(x) = \sqrt{x}– 10\) for all positive numbers x. If u = f(t) for some positive numbers t and u, what is t in terms of u? (A) \(\sqrt{\sqrt{u}+10}\) (B) \((\sqrt{u}+10)^2\) (C) \(\sqrt{u^2+10}\) (D) \((u + 10)^2\) (E) \((u^2 + 10)^2\)
Official Answer and Stats are available only to registered users. Register/ Login.
_________________
Originally posted by Bunuel on 03 May 2011, 10:00.
Last edited by Bunuel on 22 Jun 2018, 01:29, edited 3 times in total.
Renamed the topic, edited the question and added the OA.




Retired Moderator
Joined: 20 Dec 2010
Posts: 1545

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
03 May 2011, 11:18
IEsailor wrote: Looks like a simple question but somehow the answer that i am getting is not in the choices provided below ( or so i think ). Pls help
The function f is defined by f(x) = √x – 10 for all positive numbers x. If u = f(t) for some positive numbers t and u. What is t in terms of u? A. √(u+10) B. (√u + 10)^2 C. √(u2+10) D. (u + 10)^2 E. (u2 + 10)^2 Sol: \(f(x)=\sqrt{x} \hspace{2} \hspace{2} 10\) For x=t,\(f(t)=\sqrt{t}10\) Given: \(f(t)=u\) Thus, \(\sqrt{t}10=u\) \(\sqrt{t}=u+10\) Squaring both sides: \(t=(u+10)^2\) Ans: "D"




Manager
Joined: 07 Oct 2010
Posts: 127

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
03 May 2011, 11:19
Ans is D
u = f(t) = \sqrt{t}  10 Therefore, u + 10 = \sqrt{t} thus, t = \((u + t)^2\)
Hence ans D



Director
Status: There is always something new !!
Affiliations: PMI,QAI Global,eXampleCG
Joined: 08 May 2009
Posts: 821

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
03 May 2011, 11:25
straight D.
t= (u+10) ^2



Manager
Joined: 12 Oct 2009
Posts: 124
Schools: Columbia, INSEAD, RSM, LBS

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
03 May 2011, 14:04
Thank you guys, Mistook it to be Underroot( t10 )...Thanks again for all the help



Director
Joined: 01 Feb 2011
Posts: 531

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
03 May 2011, 14:53
t (in terms of u)?
u = f(t) = \sqrt{t}  10
=> u = \sqrt{t}  10 => \sqrt{t} = u +10 t = \((u+10)^2\)
Answer is D.



Intern
Joined: 03 May 2011
Posts: 1

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
03 May 2011, 15:32
IEsailor wrote: Looks like a simple question but somehow the answer that i am getting is not in the choices provided below ( or so i think ). Pls help
The function f is defined by f(x) = √x – 10 for all positive numbers x. If u = f(t) for some positive numbers t and u. What is t in terms of u? A. √(u+10) B. (√u + 10)^2 C. √(u2+10) D. (u + 10)^2 E. (u2 + 10)^2 This problem may seem confusing at first glance with all the variables thrown at you. Here is how I solved this problem: You are given main function: f(x) = \sqrt{x}  10 Then, it says "u = f(t)", which basically says "u = f(x)" and "t = x" in your main function So, from the information provided, you can rewrite the equation to be the following: u = \sqrt{t}  10 Finally, you are asked "what is t in terms of u?". Basically, solve for t. u = \sqrt{t}  10 u + 10 = \sqrt{t} (u + 10)^2 = t Answer: D Hope this helps!



Retired Moderator
Joined: 16 Nov 2010
Posts: 1232
Location: United States (IN)
Concentration: Strategy, Technology

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
05 May 2011, 07:05
f(t) = root(t)  10 = u => t = (u+10)^2 Answer  D
_________________
Formula of Life > Achievement/Potential = k * Happiness (where k is a constant) GMAT Club Premium Membership  big benefits and savings



Board of Directors
Joined: 17 Jul 2014
Posts: 2491
Location: United States (IL)
Concentration: Finance, Economics
GPA: 3.92
WE: General Management (Transportation)

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
18 Oct 2015, 13:15
ok, so we have f(t) = u rewrite this as: sqrt(t)  10 = u sqrt(t) = u+10
square everything: t=(u+10)^2 answer choice D



Manager
Joined: 01 Mar 2015
Posts: 68

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
18 Oct 2015, 22:02
Bunuel wrote: The function f is defined by \(f(x) = \sqrt{x}– 10\) for all positive numbers x. If u = f(t) for some positive numbers t and u, what is t in terms of u?
(A) \(\sqrt{\sqrt{u}+10}\) (B) \((\sqrt{u}+10)^2\) (C) \(\sqrt{u^2+10}\) (D) (u + 10)^2 (E) (u2 + 10)^2
Kudos for a correct solution. given \(f(x) = \sqrt{x}– 10\) and \(u = f(t) = \sqrt{t}– 10\) => \(u = \sqrt{t}– 10\) => \(u + 10 = \sqrt{t}\) => \((u + 10)^2 = t\) (square both sides) Answer Choice Dkudos, if you like the post



CEO
Status: GMATINSIGHT Tutor
Joined: 08 Jul 2010
Posts: 2977
Location: India
GMAT: INSIGHT
WE: Education (Education)

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
27 Oct 2015, 06:04
IEsailor wrote: The function f is defined by \(f(x) = \sqrt{x} 10\) for all positive numbers x. If u = f(t) for some positive numbers t and u. What is t in terms of u? A. \(\sqrt{u+10}\)
B. \((\sqrt{u} + 10)^2\)
C. \(\sqrt{u^2+10}\)
D. \((u + 10)^2\)
E. \((u^2 + 10)^2\) Just a motivation bosster for people afraid of Functions. Questions of Function generally require the test taker to be only obedient instead of asking them to be smart in Quant. Just follow the instructions mwnioned in question Given : f(x)= \(\sqrt{x} 10\) And u = f(t) Instruction is to compare f(x) with f(t) and find f(t) I.e. replace x by t in the expression of f(x) I.e. f(t)= \(\sqrt{t} 10\) But u = f(t) I.e. u = \(\sqrt{t} 10\) I.e. u+10 =\(\sqrt{t}\) I.e. \((u+10)^2 = t\) Answer: Option D
_________________
Prosper!!!GMATinsightBhoopendra Singh and Dr.Sushma Jha email: info@GMATinsight.com I Call us : +919999687183 / 9891333772 Online OneonOne Skype based classes and Classroom Coaching in South and West Delhihttp://www.GMATinsight.com/testimonials.htmlACCESS FREE GMAT TESTS HERE:22 ONLINE FREE (FULL LENGTH) GMAT CAT (PRACTICE TESTS) LINK COLLECTION



Director
Status: Professional GMAT Tutor
Affiliations: AB, cum laude, Harvard University (Class of '02)
Joined: 10 Jul 2015
Posts: 715
Location: United States (CA)
Age: 40
GMAT 1: 770 Q47 V48 GMAT 2: 730 Q44 V47 GMAT 3: 750 Q50 V42
WE: Education (Education)

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
Updated on: 01 Apr 2016, 19:28
The function f is defined by f( x) = \(\sqrt{x}  10\) for all positive numbers . If u = f( t) for some positive numbers t and u, what is t in terms of u?
_________________
Harvard grad and 99% GMAT scorer, offering expert, private GMAT tutoring and coaching worldwide since 2002. One of the only known humans to have taken the GMAT 5 times and scored in the 700s every time (700, 710, 730, 750, 770), including verified section scores of Q50 / V47, as well as personal bests of 8/8 IR (2 times), 6/6 AWA (4 times), 50/51Q and 48/51V. You can download my official testtaker score report (all scores within the last 5 years) directly from the Pearson Vue website: https://tinyurl.com/y7knw7bt Date of Birth: 09 December 1979. GMAT Action Plan and Free EBook  McElroy TutoringContact: mcelroy@post.harvard.edu (I do not respond to PMs on GMAT Club) or find me on reddit: http://www.reddit.com/r/GMATpreparation



Director
Status: Professional GMAT Tutor
Affiliations: AB, cum laude, Harvard University (Class of '02)
Joined: 10 Jul 2015
Posts: 715
Location: United States (CA)
Age: 40
GMAT 1: 770 Q47 V48 GMAT 2: 730 Q44 V47 GMAT 3: 750 Q50 V42
WE: Education (Education)

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
01 Apr 2016, 16:16
Attached is a visual that should help.
Attachments
Screen Shot 20160401 at 4.02.28 PM.png [ 114.92 KiB  Viewed 18214 times ]
_________________
Harvard grad and 99% GMAT scorer, offering expert, private GMAT tutoring and coaching worldwide since 2002. One of the only known humans to have taken the GMAT 5 times and scored in the 700s every time (700, 710, 730, 750, 770), including verified section scores of Q50 / V47, as well as personal bests of 8/8 IR (2 times), 6/6 AWA (4 times), 50/51Q and 48/51V. You can download my official testtaker score report (all scores within the last 5 years) directly from the Pearson Vue website: https://tinyurl.com/y7knw7bt Date of Birth: 09 December 1979. GMAT Action Plan and Free EBook  McElroy TutoringContact: mcelroy@post.harvard.edu (I do not respond to PMs on GMAT Club) or find me on reddit: http://www.reddit.com/r/GMATpreparation



Intern
Joined: 24 May 2016
Posts: 19
Location: Germany
Concentration: International Business, General Management

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
03 Jun 2017, 01:44
From the stem you clearly see it is a function question, further you read the phrase "in terms of", which should make you thinking that you should do math instead of plugging in numbers. Now when you follow the stem you get: f(x) = x√−10, leading to if you plug in t for x: f(t)=√t –10, which is equal to u. √t –10 = u, add the 10 to both sides and square both sides > t = (u+10)^2



Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 8656
Location: United States (CA)

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
19 Dec 2017, 07:44
IEsailor wrote: The function f is defined by \(f(x) = \sqrt{x} 10\) for all positive numbers x. If u = f(t) for some positive numbers t and u. What is t in terms of u? A. \(\sqrt{u+10}\)
B. \((\sqrt{u} + 10)^2\)
C. \(\sqrt{u^2+10}\)
D. \((u + 10)^2\)
E. \((u^2 + 10)^2\) We are given the function defined by f(x) = √x – 10 and we also see that f(t) = u. First, let's determine what f(t) looks like and then set the result equal to u. f(t) = √t – 10 √t – 10 = u To finish, we need to get t in terms of u. √t = u + 10 t = (u + 10)^2 Answer: D
_________________
5star 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.



Director
Joined: 17 Dec 2012
Posts: 623
Location: India

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
08 Mar 2018, 15:09
IEsailor wrote: The function f is defined by \(f(x) = \sqrt{x} 10\) for all positive numbers x. If u = f(t) for some positive numbers t and u. What is t in terms of u? A. \(\sqrt{u+10}\)
B. \((\sqrt{u} + 10)^2\)
C. \(\sqrt{u^2+10}\)
D. \((u + 10)^2\)
E. \((u^2 + 10)^2\) Main Idea: Express what is given in terms of u and t Details: f(t)=u=root(t)10 => (u+10)^2=t Hence D.
_________________
Srinivasan Vaidyaraman Sravna Test Prep http://www.sravnatestprep.comHolistic and Systematic Approach



Intern
Joined: 03 Aug 2019
Posts: 4
Location: Australia
Concentration: General Management, General Management

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
14 Aug 2019, 09:33
Bunuel wrote: The function f is defined by \(f(x) = \sqrt{x}– 10\) for all positive numbers x. If u = f(t) for some positive numbers t and u, what is t in terms of u?
(A) \(\sqrt{\sqrt{u}+10}\)
(B) \((\sqrt{u}+10)^2\)
(C) \(\sqrt{u^2+10}\)
(D) \((u + 10)^2\)
(E) \((u^2 + 10)^2\) Just substitute f(x) for u and simplify it



Intern
Status: Professional GMAT Trainer
Affiliations: GMAT Coach
Joined: 21 Mar 2017
Posts: 10
Location: United States
GMAT 1: 760 Q50 V44 GMAT 2: 770 Q51 V44

Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
Show Tags
01 Dec 2019, 21:00
Bunuel wrote: The function f is defined by \(f(x) = \sqrt{x}– 10\) for all positive numbers x. If u = f(t) for some positive numbers t and u, what is t in terms of u?
(A) \(\sqrt{\sqrt{u}+10}\)
(B) \((\sqrt{u}+10)^2\)
(C) \(\sqrt{u^2+10}\)
(D) \((u + 10)^2\)
(E) \((u^2 + 10)^2\) f(t) = \(\sqrt{t}\)  10 (We are just plugging in t wherever x appears in the function; this is how functions work. The part inside the parentheses is the input  for example, f(3z) = \(\sqrt{3z}\)  10 ) Now, the question asks "what is t"  meaning we need to get t alone u = \(\sqrt{t}\)  10 u + 10 = \(\sqrt{t}\) Now, we square both sides: \((u+10)^2\) = t > Answer is D
_________________
6 Principles for Effective GMAT Training: https://www.gmatcoach.com/ourapproach/I offer online tutoring  please visit gmatcoach.com/trial to request a free consultation.




Re: The function f is defined by f(x) = x^(1/2)  10 for all positive numb
[#permalink]
01 Dec 2019, 21:00






