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

It is currently 03 Sep 2015, 20:46
GMAT Club Tests

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, does x^y . y^(-x) = 1? (1) x^x

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Senior Manager
Senior Manager
User avatar
Joined: 04 Nov 2006
Posts: 267
Location: California
Followers: 1

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

If x and y are integers, does x^y . y^(-x) = 1? (1) x^x [#permalink] New post 20 Dec 2006, 13:55
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

If x and y are integers, does x^y . y^(-x) = 1?

(1) x^x > y

(2) x > y^y
Senior Manager
Senior Manager
avatar
Joined: 08 Jun 2006
Posts: 341
Location: Washington DC
Followers: 1

Kudos [?]: 30 [0], given: 0

 [#permalink] New post 20 Dec 2006, 17:22
Tried with few numbers ..nothing is matching ..
Going for E..
Manager
Manager
avatar
Joined: 04 Feb 2004
Posts: 71
Location: India
Followers: 1

Kudos [?]: 25 [0], given: 0

 [#permalink] New post 21 Dec 2006, 05:56
waiting for a detailed explanation - My bet is e
Senior Manager
Senior Manager
avatar
Joined: 08 Jun 2006
Posts: 341
Location: Washington DC
Followers: 1

Kudos [?]: 30 [0], given: 0

 [#permalink] New post 21 Dec 2006, 06:14
Thought of adding a question

x ^ y = y ^ x is true for (2,4) and (-2,-4).

What are the other possible combinations???
Senior Manager
Senior Manager
avatar
Joined: 23 Jun 2006
Posts: 387
Followers: 1

Kudos [?]: 312 [0], given: 0

 [#permalink] New post 21 Dec 2006, 06:35
actually, answer is B

(x^y)*(y^(-x))=1 is very rare for integers...
it can happen only if x^y=y^x

there are only few integer solutions to that:
(2,4),(4,2),(-2,-4),(-4,-2) and (a,a) for every integer a not equals to 0.

just check to see that none of the options satisfy st2. which means that if st2 is true - x and y are not one of these, and the answer to stem question is no. hence sufficient.
st1, however, can accomodate some of the solutions (and of course accomodate more different combinations). hence insufficient.

answer is B
Senior Manager
Senior Manager
avatar
Joined: 23 Jun 2006
Posts: 387
Followers: 1

Kudos [?]: 312 [0], given: 0

 [#permalink] New post 21 Dec 2006, 06:40
i stand corrected.... answer is C

st2 rules out most solutions, except solutions of the form (a,a) where a<-1
(for example x=-3 y=-3).

however, together with st1 these solutions are also ruled out.

hence we need both st1 and st2 to rule out all solutions (and answer stem question).

if we new x,y are positive (which we don't), then B would be the correct answer.
  [#permalink] 21 Dec 2006, 06:40
Display posts from previous: Sort by

If x and y are integers, does x^y . y^(-x) = 1? (1) x^x

  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®.