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

It is currently 20 Aug 2014, 06:46

Starting Soon:

Live Q&A Session with Cambridge Admissions Team   ||    Join Chat Room to Attend the Session


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 intigers is x^y * y^-x = 1?? 1) x^x > y 2)

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
SVP
SVP
User avatar
Joined: 05 Jul 2006
Posts: 1542
Followers: 5

Kudos [?]: 67 [0], given: 39

if x and y are intigers is x^y * y^-x = 1?? 1) x^x > y 2) [#permalink] New post 16 Sep 2006, 03:59
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
if x and y are intigers is x^y * y^-x = 1??

1) x^x > y
2) x>y^y
Director
Director
avatar
Joined: 13 Nov 2003
Posts: 801
Location: BULGARIA
Followers: 1

Kudos [?]: 19 [0], given: 0

GMAT Tests User
 [#permalink] New post 16 Sep 2006, 04:25
I used following
A) X^X=Y then stem is =1 but since it is inequality, then it is not = to 1
IMO it should be D
SVP
SVP
User avatar
Joined: 01 May 2006
Posts: 1816
Followers: 8

Kudos [?]: 87 [0], given: 0

GMAT Tests User
 [#permalink] New post 16 Sep 2006, 05:35
For me, it's (B)

Statment 1:
If x = y = 2, then :
> 2^2 = 4 > 2
> 2^2 / (2^2) = 1

If x = 2 and y = 1, then :
> 2^2 = 4 > 1
> 2^1 / (1^2) = 2

INSUFF

Statment 2:
x > y^y thus x > y (x & y are integers) that means x != y

Hence, x^y * y^-x != 1

SUFF
VP
VP
avatar
Joined: 28 Mar 2006
Posts: 1390
Followers: 2

Kudos [?]: 18 [0], given: 0

GMAT Tests User
Re: Excellent iniquality DS [#permalink] New post 16 Sep 2006, 06:23
yezz wrote:
if x and y are intigers is x^y * y^-x = 1??

1) x^x > y
2) x>y^y


Can some one see if my working is correct?

given x,y are ints

is x^y * y^-x = 1

or x^y / y^x = 1 ===> x^y = y^x

taking logs on both sides we have to prove (y/x)(logx/logy)=1

from (1) we have
xlogx > log y

logx/logy > 1/x

(so we do not know anything about it)

from (2) we have

x>y^y ==> logx > ylogy
Means
logx/logy > y

Then I am lost... :evil: :evil:
Director
Director
avatar
Joined: 13 Nov 2003
Posts: 801
Location: BULGARIA
Followers: 1

Kudos [?]: 19 [0], given: 0

GMAT Tests User
 [#permalink] New post 16 Sep 2006, 06:32
Hallo trivikram
think that ; or x^y / y^x = 1 ===> x^y = y^x
is NOT correct .It should be (x^y-y^x)/y^x=0 where y^x can not be 0 since division by 0 is not defined
VP
VP
avatar
Joined: 28 Mar 2006
Posts: 1390
Followers: 2

Kudos [?]: 18 [0], given: 0

GMAT Tests User
 [#permalink] New post 16 Sep 2006, 06:36
BG wrote:
Hallo trivikram
think that ; or x^y / y^x = 1 ===> x^y = y^x
is NOT correct .It should be (x^y-y^x)/y^x=0 where y^x can not be 0 since division by 0 is not defined


But BG from there how do we proceed?
VP
VP
User avatar
Joined: 21 Aug 2006
Posts: 1026
Followers: 1

Kudos [?]: 18 [0], given: 0

GMAT Tests User
Re: Excellent iniquality DS [#permalink] New post 16 Sep 2006, 07:37
yezz wrote:
if x and y are intigers is x^y * y^-x = 1??

1) x^x > y
2) x>y^y


The condition x^y * y^-x = 1 will be valid only if x and y are 2 and 4

from statement 2 we can say that, that is not the case. Hence B is the anwer.
_________________

The path is long, but self-surrender makes it short;
the way is difficult, but perfect trust makes it easy.

Senior Manager
Senior Manager
avatar
Joined: 31 May 2006
Posts: 381
Location: Phoenix AZ
Followers: 1

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

GMAT Tests User
 [#permalink] New post 16 Sep 2006, 07:44
......................... :(
SVP
SVP
User avatar
Joined: 01 May 2006
Posts: 1816
Followers: 8

Kudos [?]: 87 [0], given: 0

GMAT Tests User
 [#permalink] New post 16 Sep 2006, 08:14
mailtheguru wrote:
......................... :(


What's going on ? :)
Current Student
avatar
Joined: 28 Dec 2004
Posts: 3405
Location: New York City
Schools: Wharton'11 HBS'12
Followers: 13

Kudos [?]: 158 [0], given: 2

GMAT Tests User
 [#permalink] New post 16 Sep 2006, 08:37
for me B is sufficient...

X and Y are integers... we dont know if they are postive or negative...

x^y * y^-x=1?


(1) x^x>y

well say if x and y=2...then 2^2>2...

2^2*1/(2^2)=1; x=2, y=3 then the stem isnt equal to 1

(2)
x>y^y; so we know that |x|>|y| and they are not equal..therefore the stem will never be 1....

sufficient
Senior Manager
Senior Manager
avatar
Joined: 31 May 2006
Posts: 381
Location: Phoenix AZ
Followers: 1

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

GMAT Tests User
 [#permalink] New post 16 Sep 2006, 09:06
Fig wrote:
mailtheguru wrote:
......................... :(


What's going on ? :)


Got screwed :-D
SVP
SVP
User avatar
Joined: 01 May 2006
Posts: 1816
Followers: 8

Kudos [?]: 87 [0], given: 0

GMAT Tests User
 [#permalink] New post 16 Sep 2006, 09:12
mailtheguru wrote:
Fig wrote:
mailtheguru wrote:
......................... :(


What's going on ? :)


Got screwed :-D


It's one part of the joy of Maths (or DS? ;) ).... One time u another time someone else (this rule works with me as well ;) )
Senior Manager
Senior Manager
avatar
Joined: 31 May 2006
Posts: 381
Location: Phoenix AZ
Followers: 1

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

GMAT Tests User
 [#permalink] New post 16 Sep 2006, 10:16
Fig wrote:
mailtheguru wrote:
Fig wrote:
mailtheguru wrote:
......................... :(


What's going on ? :)


Got screwed :-D


It's one part of the joy of Maths (or DS? ;) ).... One time u another time someone else (this rule works with me as well ;) )


yeah, sure.
Where are these questiosn from?
Director
Director
User avatar
Joined: 06 May 2006
Posts: 783
Followers: 3

Kudos [?]: 14 [0], given: 0

GMAT Tests User
 [#permalink] New post 16 Sep 2006, 10:42
A very shaky B for me as well...

x^y = y^x
=> ylogx = x logy
=> y/x = logy/logx -- (1)

A# x^x > y
=> xlogx > logy
=> From (1), y/x^2 = logy/xlogx < 1
=> y < x^2

Now, if x=2, we have y = 1, 2, 3... if y = 2 then x^y = y^x, but not in the case of y =1 or 3. Hence not sufficient.

B# x > y^y
=> logx > ylogy
=> from (1), y^2/x = ylogy/logx < 1
=> y^2 < x

Now, if x = 27, we have y = 1, 2, 3, 4 or 5; but the expression in the question does not evaluate to 1 in any of the cases. Hence sufficient.
SVP
SVP
User avatar
Joined: 05 Jul 2006
Posts: 1542
Followers: 5

Kudos [?]: 67 [0], given: 39

 [#permalink] New post 16 Sep 2006, 12:15
if x and y are intigers is x^y * y^-x = 1??

1) x^x > y
2) x>y^y

rephrase stem x^y *1/y^x = 1 ie: receprocals

This is only possible if x^y = y^x and in turn this is only possible if x=y or x,y belongs to the set {2,4}

from one

x^x > y thus sure x,y are not equall one

x,y could be anything and could be x=4 and y=2 .....insuff

from two

x>y^ythus sure x,y are not equall one and sure /x/> /y/ thus if they are 2,4 x must be the 4 and thus y^y = 4....suff

because now we are sure that the only two conditions that make the assumption true are not valid ( being one or {2,4})

suff

answer is not a shaky b it is B :lol:

Last edited by yezz on 16 Sep 2006, 12:35, edited 2 times in total.
SVP
SVP
User avatar
Joined: 01 May 2006
Posts: 1816
Followers: 8

Kudos [?]: 87 [0], given: 0

GMAT Tests User
 [#permalink] New post 16 Sep 2006, 12:32
yezz wrote:
if x and y are intigers is x^y * y^-x = 1??

1) x^x > y
2) x>y^y

rephrase stem x^y *1/y^x = 1 ie: receprocals

This is only possible if x^y = y^x and in turn this is only possible if x=y=1

or x,y belongs to the set {2,4}


from one

x^x > y thus sure x,y are not equall one

x,y could be anything and could be x=4 and y=2 .....insuff

from two

x>y^ythus sure x,y are not equall one and sure /x/> /y/ thus if they are 2,4 x must be the 4 and thus y^y = 4....suff

because now we are sure that the only two conditions that make the assumption true are not valid ( being one or {2,4})

suff

answer is not a shaky b it is B :lol:


Not agree with the bold ;)

x = y makes it :) and no restricted values on it apart 0^0 (recently identified as not fitted for GMAT ;) )
SVP
SVP
User avatar
Joined: 05 Jul 2006
Posts: 1542
Followers: 5

Kudos [?]: 67 [0], given: 39

 [#permalink] New post 16 Sep 2006, 12:34
:lol: :lol: come on Fig you ve got to get over this exponent DS ...

and i agree with you on your comment but still it would be insuff

I will edit it
SVP
SVP
User avatar
Joined: 01 May 2006
Posts: 1816
Followers: 8

Kudos [?]: 87 [0], given: 0

GMAT Tests User
 [#permalink] New post 16 Sep 2006, 12:39
It's the end of my day here ;) I'm allowed to turn the end of my post to something funny for those who know it ;)
SVP
SVP
User avatar
Joined: 05 Jul 2006
Posts: 1542
Followers: 5

Kudos [?]: 67 [0], given: 39

 [#permalink] New post 16 Sep 2006, 12:41
Man GMAT is funny

funny wn we do silly mistakes " kinder garten ones" apart from the test

and funny when you laugh yourself to death infront of a hard DS that you ve no clue about

we need those jokes all the time

by the way i like your audi :wink:
SVP
SVP
User avatar
Joined: 01 May 2006
Posts: 1816
Followers: 8

Kudos [?]: 87 [0], given: 0

GMAT Tests User
 [#permalink] New post 16 Sep 2006, 12:52
Ahhh :) If u start to speak about Audi... I'm not ready to make an end to this day finally ;)

Frankly, I recommand this brand over the 2 other major german brands :) But I try to convince no one ;)
  [#permalink] 16 Sep 2006, 12:52
    Similar topics Author Replies Last post
Similar
Topics:
1 Experts publish their posts in the topic Is x < y ? (1) y/x > x/y (2) y > 100 goodyear2013 2 18 Apr 2014, 09:04
Q: Is x > y ? (1) x(x-1) > xy (2) (x-y)^3 > 0 Summer3 4 09 Mar 2007, 18:48
If x and y are integers, does x^y . y^(-x) = 1? (1) x^x mm007 5 20 Dec 2006, 13:55
Is x-y > y-x ??? 1) x+y > 0 2) x < 0 netcaesar 3 01 Nov 2006, 05:36
If x = 3y, is x^2 > y^2? 1. y+x < x-y 2. x^2 = 9 y^2 haas_mba07 4 14 Sep 2006, 05:41
Display posts from previous: Sort by

if x and y are intigers is x^y * y^-x = 1?? 1) x^x > y 2)

  Question banks Downloads My Bookmarks Reviews Important topics  

Go to page    1   2    Next  [ 21 posts ] 



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®.