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

It is currently 18 Jun 2018, 17:59

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

Is x^2 equal to xy?

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

Hide Tags

Intern
Intern
avatar
Joined: 22 Nov 2008
Posts: 20
Is x^2 equal to xy? [#permalink]

Show Tags

New post 15 Dec 2009, 23:28
6
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

71% (01:57) correct 29% (01:23) wrong based on 381 sessions

HideShow timer Statistics

Is x^2 equal to xy?

(1) x^2 – y^2 = (x + 5)(y - 5)
(2) x = y
Expert Post
2 KUDOS received
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 46129
Is x^2 equal to xy? [#permalink]

Show Tags

New post 16 Dec 2009, 06:39
2
Is x^2 equal to xy?

Question: is \(x^2=xy\)? --> \(x(x-y)=0\) --> Equation holds true if \(x=0\) or/and \(x=y\).

So, basically question asks: Is \(x=0\) or/and \(x=y\) true?

Obviously statement (2) is sufficient, as it gives directly that \(x=y\).

(1) x^2 – y^2 = (x + 5)(y - 5) --> \((x+y)(x-y)=(x + 5)(y-5)\)

If \(y=5\) --> \((x+5)(x-5)=(x+5)(5-5)\) --> \((x+5)(x-5)=0\) --> Either \(x=5=y\) and in this case answer to the question is YES OR \(x=-5\), hence \(x\) is not equal to \(y\) (nor to zero) and in this case answer to the question is NO. So two different answers.

Not sufficient.

Answer: B.
_________________

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

Intern
Intern
User avatar
Joined: 03 Mar 2010
Posts: 37
Re: Algebra DS [#permalink]

Show Tags

New post 02 Aug 2010, 08:08
Statement 1:
(x,y)=(5,5) --> x²=xy
(x,y)=(-5,5) --> x²<>xy
not sufficient

Statement 2:
x=y --> xx=xy or x²=xy
sufficient

B
_________________

Hardworkingly, you like my post, so kudos me.

1 KUDOS received
Intern
Intern
avatar
Joined: 10 Apr 2008
Posts: 21
Re: Algebra DS [#permalink]

Show Tags

New post 02 Aug 2010, 20:23
1
I agree with bogos.

Stmt1:
x^2 - y^2 = (x+5)(x-5)
x^2 - y^2 = x^2 - 25
0 = y^2 - 25
y = +5, -5

plugin a possible value of y into the equation x^2 - y^2 = x^2 - 25
you can see when that y can be -5 and x can 5. But plugging in the same value into x^2 = xy would yield 25 = -25.
Intern
Intern
avatar
Joined: 12 Oct 2009
Posts: 11
Concentration: Operations, Finance
GPA: 3.09
Re: ALGEBRA [#permalink]

Show Tags

New post 04 Oct 2010, 00:21
X=5 =>> y=+/-5
But if you substitute back in eqn only y=5 is valid

Please post OA
SVP
SVP
User avatar
Joined: 06 Sep 2013
Posts: 1885
Concentration: Finance
GMAT ToolKit User
Re: Is x^2 equal to xy? [#permalink]

Show Tags

New post 02 Feb 2014, 17:06
dobinnoli wrote:
Is x^2 equal to xy?

(1) x^2 – y^2 = (x + 5)(y - 5)
(2) x = y


Is x(x-y)=0

So is x=0 or x=y?

Statement 1

Obviously x is not equal to y otherwise LHS and RHS should be zero

Is x = 0

Is -y^2 = -25, could be but we don't know

Statement 2

x=y, yes. This is correct and sufficient

B
Senior Manager
Senior Manager
User avatar
S
Joined: 08 Dec 2015
Posts: 304
GMAT 1: 600 Q44 V27
Reviews Badge
Re: Is x^2 equal to xy? [#permalink]

Show Tags

New post 26 Jun 2016, 06:41
Omg, can someone please post detailed explanation for this one? I don't understand why are we using Y=5 to evaluate the (x+y)(x-y)=(x+5)(y-5) why not use 10 or 40 or something else? why 5? Does it have something to do with question stem?

Im totally confused here
Intern
Intern
User avatar
Joined: 11 Apr 2015
Posts: 35
Location: Germany
Concentration: General Management, Entrepreneurship
GPA: 3.1
WE: Project Management (Energy and Utilities)
Re: Is x^2 equal to xy? [#permalink]

Show Tags

New post 08 Jul 2016, 03:42
iliavko wrote:
Omg, can someone please post detailed explanation for this one? I don't understand why are we using Y=5 to evaluate the (x+y)(x-y)=(x+5)(y-5) why not use 10 or 40 or something else? why 5? Does it have something to do with question stem?

Im totally confused here



I guess we are using 5 in order to make (x+y)(x-y) = 0, which is the easiest way to figure out the possible values of x
_________________

"I fear not the man who has practiced 10,000 kicks once, but I fear the man who has practiced one kick 10,000 times." Bruce Lee

"I hated every minute of training, but I said, "Don’t quit. Suffer now and live the rest of your life as a champion."" Muhammad Ali

Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 6995
Premium Member
Re: Is x^2 equal to xy? [#permalink]

Show Tags

New post 11 Feb 2018, 13:03
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

Re: Is x^2 equal to xy?   [#permalink] 11 Feb 2018, 13:03
Display posts from previous: Sort by

Is x^2 equal to xy?

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


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®.