Find all School-related info fast with the new School-Specific MBA Forum

It is currently 10 Jul 2014, 08:39

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If x and y are integers and xy does not equal 0, is xy <

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
avatar
Joined: 09 Apr 2008
Posts: 53
Followers: 0

Kudos [?]: 4 [0], given: 4

If x and y are integers and xy does not equal 0, is xy < [#permalink] New post 28 Sep 2008, 22:45
If x and y are integers and xy does not equal 0, is xy < 0?

(1) y = x^4 – x^3

(2) x is to the right of y on the number line


-----------
Question is asking if x, y have different signs.

For 1) y = x^3(x-1)

if x < 0, x^3 < 0 and x-1 < 0. So y is positive.
if x > 0, x^3 > 0 and x-1 > 0. So y is positive.

Hence INSUFF.

For 2) x > y. This doesn't tell us anything.

So taking the two together...

y > 0 and x > y

BUT this isn't possible!?

x > y (=x^3(x-1))

x > x^3(x-1)
x>0 so

1 > x^2 (x-1)

there is no solution to this inequality where x is an int and greater than 0. So the answer should be INSUFF??
Director
Director
avatar
Joined: 23 Sep 2007
Posts: 799
Followers: 5

Kudos [?]: 72 [0], given: 0

GMAT Tests User
Re: MGMAT CAT question - difficult one. [#permalink] New post 29 Sep 2008, 00:04
thinkblue wrote:
If x and y are integers and xy does not equal 0, is xy < 0?

(1) y = x^4 – x^3

(2) x is to the right of y on the number line


C

statement 1: x can be positive or negative, but y is positive, insuff

statement 2: x is bigger than y, insuff

together = suff
Manager
Manager
avatar
Joined: 23 Apr 2008
Posts: 90
Followers: 1

Kudos [?]: 5 [0], given: 0

Re: MGMAT CAT question - difficult one. [#permalink] New post 29 Sep 2008, 04:31
IMO C

1.y = x^4 - x^3

in this case y will always be positive,no matter what the sign of 'x' is
but we dont know anything about the sign of 'x'
SO INSUFFICIENT

2.INSUFFICIENT because it also yields two results

1&2. SUFFICIENT
from 1 we know that 'y' is positive and if 'x' lies to the right of 'y',then 'x' shud be positive too.

hence xy>0
answer is NO
Senior Manager
Senior Manager
User avatar
Joined: 29 Mar 2008
Posts: 350
Followers: 3

Kudos [?]: 40 [0], given: 0

GMAT Tests User
Re: MGMAT CAT question - difficult one. [#permalink] New post 29 Sep 2008, 10:19
Agree with (C)

(I) Tells us y is positive whatever the value of x is.
x can be +ve or -Ve, Hence Insuff.
(II) Tess us that x>y. Both can be negative, positive or one negative and the other positive (vice versa). Not Suff

I and II together. Y is positive from I, x>y from II, Hence x and y are bothe +ve.
Therefore, xy<0 is False. Suff.
_________________

To find what you seek in the road of life, the best proverb of all is that which says:
"Leave no stone unturned."
-Edward Bulwer Lytton

SVP
SVP
avatar
Joined: 17 Jun 2008
Posts: 1580
Followers: 11

Kudos [?]: 170 [0], given: 0

GMAT Tests User
Re: MGMAT CAT question - difficult one. [#permalink] New post 29 Sep 2008, 12:04
C.

From stmt 1, y = x^3(x-1)....here x does not equal 0 and 1 otherwise xy will become 0.
Hence, if x > 0, y will always be >0. and if x < 0, y will again be >0. Hence ,insufficient.

Combining this with stmt2, only possibility is of x>0 and y>0. Hence, sufficient.
Intern
Intern
avatar
Joined: 29 Sep 2008
Posts: 47
Followers: 0

Kudos [?]: 8 [0], given: 0

Re: MGMAT CAT question - difficult one. [#permalink] New post 29 Sep 2008, 13:54
I have a feeling that it should be E.
Reason:
when you combine I and II, we are left with two conflicting cases:
case 1: x is between 0 and 1 which makes y < 0 and product negative
case 2: x is greater than 1 (which makes y > 0) and at some point between 1 and 2 which makes x > y (its important to note that for values of x around 2 or more, x is always less than y). product is positive.

Thus E.

I have to say that this took me a long time and I would have guessed in the real test, or maybe I am missing some trick. is the OA C?
Manager
Manager
avatar
Joined: 09 Apr 2008
Posts: 53
Followers: 0

Kudos [?]: 4 [0], given: 4

Re: MGMAT CAT question - difficult one. [#permalink] New post 29 Sep 2008, 16:46
aim2010 wrote:
I have a feeling that it should be E.
Reason:
when you combine I and II, we are left with two conflicting cases:
case 1: x is between 0 and 1 which makes y < 0 and product negative
case 2: x is greater than 1 (which makes y > 0) and at some point between 1 and 2 which makes x > y (its important to note that for values of x around 2 or more, x is always less than y). product is positive.

Thus E.

I have to say that this took me a long time and I would have guessed in the real test, or maybe I am missing some trick. is the OA C?


And that is the whole problem. There is NO value of x for which it can be an int, positive and greater than 1, AND greater than y.
SVP
SVP
avatar
Joined: 17 Jun 2008
Posts: 1580
Followers: 11

Kudos [?]: 170 [0], given: 0

GMAT Tests User
Re: MGMAT CAT question - difficult one. [#permalink] New post 29 Sep 2008, 21:53
aim2010 wrote:
I have a feeling that it should be E.
Reason:
when you combine I and II, we are left with two conflicting cases:
case 1: x is between 0 and 1 which makes y < 0 and product negative
case 2: x is greater than 1 (which makes y > 0) and at some point between 1 and 2 which makes x > y (its important to note that for values of x around 2 or more, x is always less than y). product is positive.

Thus E.

I have to say that this took me a long time and I would have guessed in the real test, or maybe I am missing some trick. is the OA C?



While we are awaiting OA, I think for any value of x > 1, difference between x^4 and x^3 will always be greater than x. I tried with value of x = 1.01 and got this true. Not sure whether there is any such mathematical rule. Can someone confirm please?
Senior Manager
Senior Manager
avatar
Joined: 18 Jun 2007
Posts: 299
Followers: 2

Kudos [?]: 15 [0], given: 0

GMAT Tests User
Re: MGMAT CAT question - difficult one. [#permalink] New post 30 Sep 2008, 02:14
St1. since x is integer x^4 -x^3 will always be positive but we dont know the sign of y so insuff.
St2 is insuff. since it doesn't tell us abt x

combine: y is positive and since x is on the riht side of y it too ought to be positive. now even if x is 0 or 1 xy would be equal to 1 and not less then 0 so answer is C.
GMAT Instructor
avatar
Joined: 04 Jul 2006
Posts: 1271
Location: Madrid
Followers: 23

Kudos [?]: 111 [0], given: 0

Re: MGMAT CAT question - difficult one. [#permalink] New post 30 Sep 2008, 02:44
If x and y are integers and xy does not equal 0, is xy < 0?

(1) y = x^4 – x^3

(2) x is to the right of y on the number line

This question looks defective. Check the wording of statement (2)
Senior Manager
Senior Manager
avatar
Joined: 18 Jun 2007
Posts: 299
Followers: 2

Kudos [?]: 15 [0], given: 0

GMAT Tests User
Re: MGMAT CAT question - difficult one. [#permalink] New post 30 Sep 2008, 06:23
kevincan wrote:
If x and y are integers and xy does not equal 0, is xy < 0?

(1) y = x^4 – x^3

(2) x is to the right of y on the number line

This question looks defective. Check the wording of statement (2)

kevin, why do you think that wording in 2nd statement can be wrong?

question stem clearly says that x y are integers and this makes y either 0 or more than 0
2nd statement says that y < x
combining both statements make xy either 0 or more than 0. and this gives the anser of the question that is xy < 0 .....suff.

Am I missing something?
GMAT Instructor
avatar
Joined: 04 Jul 2006
Posts: 1271
Location: Madrid
Followers: 23

Kudos [?]: 111 [0], given: 0

Re: MGMAT CAT question - difficult one. [#permalink] New post 30 Sep 2008, 06:49
If y=x^4 - x^3 and x and y are non-zero integers , how can x be greater than y?
Intern
Intern
avatar
Joined: 29 Sep 2008
Posts: 47
Followers: 0

Kudos [?]: 8 [0], given: 0

Re: MGMAT CAT question - difficult one. [#permalink] New post 30 Sep 2008, 07:06
aim2010 wrote:
I have a feeling that it should be E.
Reason:
when you combine I and II, we are left with two conflicting cases:
case 1: x is between 0 and 1 which makes y < 0 and product negative
case 2: x is greater than 1 (which makes y > 0) and at some point between 1 and 2 which makes x > y (its important to note that for values of x around 2 or more, x is always less than y). product is positive.

Thus E.

I have to say that this took me a long time and I would have guessed in the real test, or maybe I am missing some trick. is the OA C?


This might be confusing. i forgot that x and y are integers. regardless, the inequality has no solution so IMO answer should be E.
@ scthakur - i cannot think of a rule, this function is a parabola which intersects the line y=x somewhere between 1 and 2. just to prove that i spent too much time on this question. (note to self - give up after 3 minutes!!)
Senior Manager
Senior Manager
avatar
Joined: 18 Jun 2007
Posts: 299
Followers: 2

Kudos [?]: 15 [0], given: 0

GMAT Tests User
Re: MGMAT CAT question - difficult one. [#permalink] New post 30 Sep 2008, 07:46
kevincan wrote:
If y=x^4 - x^3 and x and y are non-zero integers , how can x be greater than y?


yup...agree. There is some problem with wordings.
Thx kevin.
Re: MGMAT CAT question - difficult one.   [#permalink] 30 Sep 2008, 07:46
    Similar topics Author Replies Last post
Similar
Topics:
1 If x and y are integers and xy does not equal 0, is xy < 0? manalq8 3 19 Nov 2011, 11:21
3 Experts publish their posts in the topic If x does not equal y, and xy does not equal 0, then when x Phaser 7 02 Nov 2010, 00:48
17 Experts publish their posts in the topic If |x| - |y| = |x+y| and xy does not equal to 0, which of divakarbio7 36 13 Jul 2010, 22:00
If x and y are integers and xy does not equal 0, is xy < lbsgmat 9 09 Aug 2009, 04:02
If x and y are integers and xy does not equal 0, is xy < sujayb 3 22 Nov 2006, 12:23
Display posts from previous: Sort by

If x and y are integers and xy does not equal 0, is xy <

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

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®.