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

It is currently 17 Jul 2018, 06:51

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

What is the value of x? 1) x^-4x=1 2) x^-x=1

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

Hide Tags

Expert Post
Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 5839
GMAT 1: 760 Q51 V42
GPA: 3.82
Premium Member
What is the value of x? 1) x^-4x=1 2) x^-x=1 [#permalink]

Show Tags

New post 29 Sep 2017, 01:26
00:00
A
B
C
D
E

Difficulty:

  65% (hard)

Question Stats:

45% (00:34) correct 55% (00:48) wrong based on 33 sessions

HideShow timer Statistics

[GMAT math practice question]

What is the value of x?

1) \(x^{-4x}\)=1
2) \(x^{-x}\)=1

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $99 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

PS Forum Moderator
avatar
D
Joined: 25 Feb 2013
Posts: 1182
Location: India
GPA: 3.82
GMAT ToolKit User Premium Member Reviews Badge
What is the value of x? 1) x^-4x=1 2) x^-x=1 [#permalink]

Show Tags

New post Updated on: 01 Oct 2017, 20:13
MathRevolution wrote:
[GMAT math practice question]

What is the value of x?

1) \(x^{-4x}\)=1
2) \(x^{-x}\)=1


Statement 1: there are two possible values of \(x\), \(x=1\) or \(x=-1\). Hence insufficient

Statement 2: implies that \(x^{-x}=1\), only one possible solution \(x=1\). Hence sufficient

Option B

Originally posted by niks18 on 29 Sep 2017, 04:56.
Last edited by niks18 on 01 Oct 2017, 20:13, edited 1 time in total.
Expert Post
Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 5839
GMAT 1: 760 Q51 V42
GPA: 3.82
Premium Member
Re: What is the value of x? 1) x^-4x=1 2) x^-x=1 [#permalink]

Show Tags

New post 01 Oct 2017, 18:19
=>
Forget conventional ways of solving math questions. In DS, VA (Variable Approach) method is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.
In the original condition, there is 1 variable(x), which should match with the number of equations. So you need 1 equation. For 1) 1 equation, for 2) 1 equation, which is likely to make D the answer.

Condition 1)
We have 2 possible values, which are x = 1 and x = -1.
This is not sufficient.

Condition 2)
The only possible value is x = 1.

Therefore, the answer is B unlike our expectation.
For cases where we need 1 more equation, such as original conditions with “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 59 % chance that D is the answer, while A or B has 38% chance and C or E has 3% chance. Since D is most likely to be the answer using 1) and 2) separately according to DS definition. Obviously there may be cases where the answer is A, B, C or E.

Answer: B
_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $99 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

Re: What is the value of x? 1) x^-4x=1 2) x^-x=1   [#permalink] 01 Oct 2017, 18:19
Display posts from previous: Sort by

What is the value of x? 1) x^-4x=1 2) x^-x=1

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

Events & Promotions

PREV
NEXT


GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| 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®.