It is currently 12 Dec 2017, 21:39

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

What is the value of x?

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

Hide Tags

1 KUDOS received
Intern
Intern
avatar
B
Joined: 30 Jun 2014
Posts: 38

Kudos [?]: 20 [1], given: 76

What is the value of x? [#permalink]

Show Tags

New post 01 May 2015, 05:32
1
This post received
KUDOS
7
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

61% (01:16) correct 39% (01:34) wrong based on 120 sessions

HideShow timer Statistics

What is the value of x?

(1) \(x^2+x+10=16\)
(2) \(x=4y^4+2y^2+2\)

Could an Expert please help with the difficulty level as well? I'm not sure if this falls in 600-700.
[Reveal] Spoiler: OA

Kudos [?]: 20 [1], given: 76

Expert Post
3 KUDOS received
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 42575

Kudos [?]: 135412 [3], given: 12692

Re: What is the value of x? [#permalink]

Show Tags

New post 01 May 2015, 06:23
3
This post received
KUDOS
Expert's post
1
This post was
BOOKMARKED
Shalabh09 wrote:
What is the value of x?

(1) \(x^2+x+10=16\)
(2) \(x=4y^4+2y^2+2\)

Could an Expert please help with the difficulty level as well? I'm not sure if this falls in 600-700.


What is the value of x?

(1) \(x^2+x+10=16\) --> \(x^2+x-6=0\) --> x=-3 or x=2. Not sufficient.

(2) \(x=4y^4+2y^2+2\). Without knowing the value of y we cannot get the value of x. Not sufficient.
Notice that from this statement it follows that x must be positive: \(x=4y^4+2y^2+2=(nonnegative)+(nonnegative)+(positive)=positive\).

(1)+(2) Since from (2) x is positive, then from (1) we are left with x=2. Sufficient.

Answer: C.

P.S. As for the difficulty level, I'd say it's ~550-600 level question.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Kudos [?]: 135412 [3], given: 12692

Expert Post
1 KUDOS received
EMPOWERgmat Instructor
User avatar
P
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 10379

Kudos [?]: 3683 [1], given: 173

Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Re: What is the value of x? [#permalink]

Show Tags

New post 01 May 2015, 14:09
1
This post received
KUDOS
Expert's post
Hi Shalabh09,

The GMAT often finds ways to test you on concepts that you know, but in ways that you're not used to thinking about. This question isn't too difficult (I'd rank it in the low-600s), but it does test you on Quadratics in ways that you're probably not used to thinking about.

Bunuel's explanation showcases the necessary "math" involved, so I won't rehash any of that here. Instead, I'll talk about the 'patterns' that you're supposed to spot in the construction of this question.

First, we're asked for the value of X. This is a standard question to ask in DS.

Second, Fact 1 gives us what appears to be a Quadratic equation with some extra "math" thrown in. You're probably used to solving Quadratic equations when they are set equal to 0..... so do the necessary math to set THIS equation equal to 0 and solve. You'll find that there are 2 solutions: X = -3 and X = 2. Fact 1 is INSUFFICIENT

Third, Fact 2 shows us that X is based on the value of Y. Since Y could be ANY value, there are multiple values for X. Fact 2 is INSUFFICIENT. There IS another thing worth noting about Fact 2 though...Notice the "even powers".....no matter what value you plug in for Y, the value of X will ALWAYS be POSITIVE.....

Combined, we know.....
X = -3 or X = 2
X will ALWAYS be positive

Combined, SUFFICIENT

Final Answer:
[Reveal] Spoiler:
C


GMAT assassins aren't born, they're made,
Rich
_________________

760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free
  Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Kudos [?]: 3683 [1], given: 173

Director
Director
User avatar
Joined: 07 Aug 2011
Posts: 578

Kudos [?]: 562 [0], given: 75

Concentration: International Business, Technology
GMAT 1: 630 Q49 V27
GMAT ToolKit User
What is the value of x? [#permalink]

Show Tags

New post 03 May 2015, 06:27
Bunuel wrote:
Shalabh09 wrote:
What is the value of x?

(1) \(x^2+x+10=16\)
(2) \(x=4y^4+2y^2+2\)

Could an Expert please help with the difficulty level as well? I'm not sure if this falls in 600-700.


What is the value of x?

(1) \(x^2+x+10=16\) --> \(x^2+x-6=0\) --> x=-3 or x=2. Not sufficient.

(2) \(x=4y^4+2y^2+2\). Without knowing the value of y we cannot get the value of x. Not sufficient.
Notice that from this statement it follows that x must be positive: \(x=4y^4+2y^2+2=(nonnegative)+(nonnegative)+(positive)=positive\).

(1)+(2) Since from (2) x is positive, then from (1) we are left with x=2. Sufficient.

Answer: C.

P.S. As for the difficulty level, I'd say it's ~550-600 level question.


Hi Bunuel

There is no information given about Y , Y can be a complex number too, so shouldn't i choose answer E ?

The roots of the polynomial \(4y^4+2y^2+5=0\) are:
\(Y_1=0.6588+0.82705∗i\)
\(Y_2=0.6588−0.82705∗i\)
\(Y_3=−0.6588+0.82705∗i\)
\(Y_4=−0.6588−0.82705∗i\)

Generally i have seen that GMAT questions always give hints about the numbers, in this question nothing has been told about Y,Strange.

noticed that there are a few questions floating in gmatclub , testing knowledge on complex numbers...
eg : if-the-square-of-the-sum-of-the-roots-of-a-quadratic-equation-197205.html
_________________

Thanks,
Lucky

_______________________________________________________
Kindly press the Image to appreciate my post !! :-)

Kudos [?]: 562 [0], given: 75

Intern
Intern
avatar
B
Joined: 30 Jun 2014
Posts: 38

Kudos [?]: 20 [0], given: 76

Re: What is the value of x? [#permalink]

Show Tags

New post 03 May 2015, 07:08
Hi Bunuel & EMPOWERgmatRichC,

Thank you very much for your detailed explanations. I guess it was just a new type of question so startled me a bit. Once the catch, which you both have shown, is seen it becomes quite simple.

Moreover, I guess due to these gaps I'm still stuck at Q41/42. I need some resources to practice such concepts. Could you guide me in this direction too?

Lucky : I read in one other forum, GMAT always deals with real numbers. So, there is no concept of complex numbers here. Hope this helps as well.

Thank you again.

Best Regards,
Shalabh.

Kudos [?]: 20 [0], given: 76

Director
Director
User avatar
Joined: 07 Aug 2011
Posts: 578

Kudos [?]: 562 [0], given: 75

Concentration: International Business, Technology
GMAT 1: 630 Q49 V27
GMAT ToolKit User
What is the value of x? [#permalink]

Show Tags

New post 03 May 2015, 07:28
Shalabh09 wrote:
Hi Bunuel & EMPOWERgmatRichC,

Thank you very much for your detailed explanations. I guess it was just a new type of question so startled me a bit. Once the catch, which you both have shown, is seen it becomes quite simple.

Moreover, I guess due to these gaps I'm still stuck at Q41/42. I need some resources to practice such concepts. Could you guide me in this direction too?

Lucky : I read in one other forum, GMAT always deals with real numbers. So, there is no concept of complex numbers here. Hope this helps as well.

Thank you again.

Best Regards,
Shalabh.


i am aware . what i am trying to say is that GMAT questions always are always unambiguous such that even you do not read the official disclaimers (eg: GMAT always tests real numbers ) , you will be able to arrive a definitive conclusion.
_________________

Thanks,
Lucky

_______________________________________________________
Kindly press the Image to appreciate my post !! :-)

Kudos [?]: 562 [0], given: 75

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 42575

Kudos [?]: 135412 [0], given: 12692

Re: What is the value of x? [#permalink]

Show Tags

New post 03 May 2015, 10:52
Lucky2783 wrote:
Bunuel wrote:
Shalabh09 wrote:
What is the value of x?

(1) \(x^2+x+10=16\)
(2) \(x=4y^4+2y^2+2\)

Could an Expert please help with the difficulty level as well? I'm not sure if this falls in 600-700.


What is the value of x?

(1) \(x^2+x+10=16\) --> \(x^2+x-6=0\) --> x=-3 or x=2. Not sufficient.

(2) \(x=4y^4+2y^2+2\). Without knowing the value of y we cannot get the value of x. Not sufficient.
Notice that from this statement it follows that x must be positive: \(x=4y^4+2y^2+2=(nonnegative)+(nonnegative)+(positive)=positive\).

(1)+(2) Since from (2) x is positive, then from (1) we are left with x=2. Sufficient.

Answer: C.

P.S. As for the difficulty level, I'd say it's ~550-600 level question.


Hi Bunuel

There is no information given about Y , Y can be a complex number too, so shouldn't i choose answer E ?

The roots of the polynomial \(4y^4+2y^2+5=0\) are:
\(Y_1=0.6588+0.82705∗i\)
\(Y_2=0.6588−0.82705∗i\)
\(Y_3=−0.6588+0.82705∗i\)
\(Y_4=−0.6588−0.82705∗i\)

Generally i have seen that GMAT questions always give hints about the numbers, in this question nothing has been told about Y,Strange.

noticed that there are a few questions floating in gmatclub , testing knowledge on complex numbers...
eg : if-the-square-of-the-sum-of-the-roots-of-a-quadratic-equation-197205.html


All numbers used on the GMAT are real numbers by default.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Kudos [?]: 135412 [0], given: 12692

Expert Post
EMPOWERgmat Instructor
User avatar
P
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 10379

Kudos [?]: 3683 [0], given: 173

Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Re: What is the value of x? [#permalink]

Show Tags

New post 04 May 2015, 12:53
Hi Shalabh09,

With a Q41 or Q42, your "issue(s)" might not be with content knowledge but in how you "see" (and respond to) the GMAT. It might be that you actually need to focus more on tactics, pattern-matching, etc. and less on doing more of the same things that you've already done.

1) How long have you studied?
2) What practice resources have you used so far?
3) What is your goal score?

GMAT assassins aren't born, they're made,
Rich
_________________

760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free
  Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Kudos [?]: 3683 [0], given: 173

Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 14883

Kudos [?]: 287 [0], given: 0

Premium Member
Re: What is the value of x? [#permalink]

Show Tags

New post 29 Oct 2017, 08:58
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 [?]: 287 [0], given: 0

Re: What is the value of x?   [#permalink] 29 Oct 2017, 08:58
Display posts from previous: Sort by

What is the value of x?

  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®.