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

It is currently 18 Jan 2019, 08:12

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 in January
PrevNext
SuMoTuWeThFrSa
303112345
6789101112
13141516171819
20212223242526
272829303112
Open Detailed Calendar
  • Free GMAT Strategy Webinar

     January 19, 2019

     January 19, 2019

     07:00 AM PST

     09:00 AM PST

    Aiming to score 760+? Attend this FREE session to learn how to Define your GMAT Strategy, Create your Study Plan and Master the Core Skills to excel on the GMAT.
  • FREE Quant Workshop by e-GMAT!

     January 20, 2019

     January 20, 2019

     07:00 AM PST

     07:00 AM PST

    Get personalized insights on how to achieve your Target Quant Score.

Is xy>0?

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

Hide Tags

 
Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 6815
GMAT 1: 760 Q51 V42
GPA: 3.82
Premium Member
Is xy>0?  [#permalink]

Show Tags

New post 28 Aug 2018, 01:06
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

74% (01:14) correct 26% (00:49) wrong based on 50 sessions

HideShow timer Statistics

[Math Revolution GMAT math practice question]

Is \(xy>0\)?

\(1) x+y>0\)
\(2) |x|+|y|<1\)

_________________

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 $149 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

Director
Director
User avatar
P
Joined: 18 Jul 2018
Posts: 570
Location: India
Concentration: Finance, Marketing
WE: Engineering (Energy and Utilities)
Premium Member Reviews Badge CAT Tests
Re: Is xy>0?  [#permalink]

Show Tags

New post 28 Aug 2018, 01:44
1
From statement 1:

No info about X and Y.
If X is +0.9 and Y is -0.4 Then X+Y = 0.5>0
But XY<0 and,
If X = 1 and Y is 2 then X+Y = 3>0
and XY>0. Both cases possible.
Insufficient.

From statement 2:

|x|+|y|<1
|X|<1 and |Y|<1
Same cases as statement 1.
Insufficient.

Combining also doesn't give a unique answer.

E is the answer.
_________________

If you are not badly hurt, you don't learn. If you don't learn, you don't grow. If you don't grow, you don't live. If you don't live, you don't know your worth. If you don't know your worth, then what's the point?

CEO
CEO
User avatar
D
Joined: 11 Sep 2015
Posts: 3332
Location: Canada
Re: Is xy>0?  [#permalink]

Show Tags

New post 28 Aug 2018, 07:11
Top Contributor
MathRevolution wrote:
[Math Revolution GMAT math practice question]

Is \(xy>0\)?

\(1) x+y>0\)
\(2) |x|+|y|<1\)


Target question: Is xy>0?

Statement 1: x + y > 0
This statement doesn't FEEL sufficient, so I'll TEST some values.
There are several values of x and y that satisfy statement 1. Here are two:
Case a: x = 1 and y = 1. In this case, xy = (1)(1) = 1. So, the answer to the target question is YES, xy IS greater than 0
Case b: x = 2 and y = -1. In this case, xy = (2)(-1) = -2. So, the answer to the target question is NO, xy is NOT greater than 0
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Aside: For more on this idea of testing values when a statement doesn't feel sufficient, read my article: http://www.gmatprepnow.com/articles/dat ... lug-values

Statement 2: |x| + |y| < 1
Let's test values again.
Case a: x = 0.2 and y = 0.2. In this case, xy = (0.2)(0.2) = 0.04. So, the answer to the target question is YES, xy IS greater than 0
Case b: x = -0.8 and y = 0.1. In this case, xy = (-0.8)(0.1) = -0.08. So, the answer to the target question is NO, xy is NOT greater than 0
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
There are still several values of x and y that satisfy BOTH statements. Here are two:
Case a: x = 0.2 and y = 0.2. In this case, xy = (0.2)(0.2) = 0.04. So, the answer to the target question is YES, xy IS greater than 0
Case b: x = 0.8 and y = -0.1. In this case, xy = (0.8)(-0.1) = -0.08. So, the answer to the target question is NO, xy is NOT greater than 0
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Answer: E

Cheers,
Brent
_________________

Test confidently with gmatprepnow.com
Image

Senior Manager
Senior Manager
User avatar
S
Joined: 07 Oct 2017
Posts: 260
Re: Is xy>0?  [#permalink]

Show Tags

New post 28 Aug 2018, 07:49
MathRevolution wrote:
[Math Revolution GMAT math practice question]

Is \(xy>0\)?

\(1) x+y>0\)
\(2) |x|+|y|<1\)
Answer is E
Attachment:
1535471463904.jpg
1535471463904.jpg [ 51.71 KiB | Viewed 454 times ]


Thank you = Kudos
_________________

Thank you =Kudos
The best thing in life lies on the other side of the pain.

Manager
Manager
User avatar
S
Joined: 06 Nov 2016
Posts: 62
Location: Viet Nam
Concentration: Strategy, International Business
GPA: 3.54
Re: Is xy>0?  [#permalink]

Show Tags

New post 28 Aug 2018, 08:56
MathRevolution wrote:
[Math Revolution GMAT math practice question]

Is \(xy>0\)?

\(1) x+y>0\)
\(2) |x|+|y|<1\)

I think the quickest way to solve this question is number plugging.
When the question is whether xy > 0 or xy < 0, I usually select number 0 to test the statement.

(1) x+y>0. If x=0, y=0.5 -> No. If x=0.1, y=0.5 -> Yes. --> Not sufficient.
(2) |x|+|y|<1. If x=0, y=0.5 -> No. If x=0.1, y=0.5 -> Yes. --> Not sufficient.

(1) + (2) Two possible answers still exist. --> Not sufficient.

Answer E.
_________________

(^人^)
Image

GMATCLUB Search for tags

GMAC © Official Guides - The Master Directory + Links

Question Directory by Topic & Difficulty
Problem Solving | Data Sufficiency | Sentence Correction | Critical Reasoning | Reading Comprehension

ONLINE FREE (FULL LENGTH) GMAT CAT (PRACTICE TESTS) LINK COLLECTION

Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 6815
GMAT 1: 760 Q51 V42
GPA: 3.82
Premium Member
Re: Is xy>0?  [#permalink]

Show Tags

New post 29 Aug 2018, 23:49
=>

Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.

Since we have 2 variables (\(x\) and \(y\)) and \(0\) equations, C is most likely to be the answer. So, we should consider conditions 1) & 2) together first. After comparing the number of variables and the number of equations, we can save time by considering conditions 1) & 2) together first.

Conditions 1) & 2)
If \(x = \frac{1}{2}\) and \(y = \frac{1}{4}\), then \(xy > 0\) and the answer is ‘yes’.
If \(x = \frac{1}{2}\) and \(y = -(\frac{1}{4})\), then \(xy < 0\) and the answer is ‘no’.

Since the answer is not unique, both conditions are not sufficient, when taken together.

Therefore, E is the answer.
Answer: E

_________________

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 $149 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

GMAT Club Bot
Re: Is xy>0? &nbs [#permalink] 29 Aug 2018, 23:49
Display posts from previous: Sort by

Is xy>0?

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


Copyright

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®.