It is currently 25 Sep 2017, 08:26

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

S is a set of positive integers such that if integer x

  post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Intern
Intern
avatar
Joined: 29 Sep 2008
Posts: 7

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

S is a set of positive integers such that if integer x [#permalink]

Show Tags

New post 06 Dec 2008, 17:17
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

My GMAT book left out the answer to this one. If someone could help me out with an explanation that would be great. Thanks!

S is a set of positive integers such that if integer x is a member of S, then both x^2 and x^3 are also in S. If the only member of S that is neither the square nor the cube of another member of S is called the source integer, is 8 in S?

1) 4 is in S and is not the source integer.

2) 64 is in S and is not the source integer.

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

Manager
Manager
User avatar
Joined: 23 Nov 2008
Posts: 78

Kudos [?]: 57 [0], given: 0

Re: Is 8 in S [#permalink]

Show Tags

New post 06 Dec 2008, 17:26
I would go with A

1) If 4 is not the source, then 4=a square or a cube of another member.
Since the set only contains positive intergers, 2 will have to be that member.
Hence, 8 is in S (2^3)

2) If 64 is in S, possible that 4 is the source, and hence 8 may not be in the set (4^2 =16, 4^3=64). or its also possible that 2 is the source, in which case 8 would be in S. Hence INSUFF.

=> A

Kudos [?]: 57 [0], given: 0

Senior Manager
Senior Manager
avatar
Joined: 30 Nov 2008
Posts: 485

Kudos [?]: 351 [0], given: 15

Schools: Fuqua
Re: Is 8 in S [#permalink]

Show Tags

New post 06 Dec 2008, 21:57
I would go with D. Here is my explanation.

S is a set of all positive integers x,y and z where y = x^2 and z = x^3 for differnt values of x. And y and z are the sources from x.

Clue 1, 4 is in the set and since it is not the source, 2 and 8 will not be in the S(if 2 is included in the set then 4 and 8 also must be included in the set and that makes 4 to be source). Self Sufficient.

Clue 2, 64 is in the set and since it is not the source, 4 and 8 will not be in the S(sqrt and cube root of 64 should not be in the S).

From either of clues, we can say that 8 will not be in the set S.

Kudos [?]: 351 [0], given: 15

Manager
Manager
avatar
Joined: 27 May 2008
Posts: 199

Kudos [?]: 45 [0], given: 0

Re: Is 8 in S [#permalink]

Show Tags

New post 06 Dec 2008, 22:17
Agre with A

1) clearly says 4 is not the source, so 2 should be the source. in tht case S will have 4,8 SUFF

2) 64 is not a source. clearly 64 is the cube root of 4 and square root of 8 so we cant say either 4 or 8 is the source. so INSUFF

Kudos [?]: 45 [0], given: 0

Intern
Intern
avatar
Joined: 01 Dec 2008
Posts: 27

Kudos [?]: [0], given: 1

Schools: Stern, Fuqua
Re: Is 8 in S [#permalink]

Show Tags

New post 09 Dec 2008, 13:18
If the only member of S that is neither the square nor the cube of another member of S is called the source integer, is 8 in S?

If 64 is in and is not the source, then it is the square or a cube of a number in it. That would mean that 4 or 8 would have to be in. and if 4 is in and not the source , then wouldn't 2 have to be in too? So if 2 is in, 8 is in, and we needed to know that both 64 and 4 weren't the source...so the answer should be C

Kudos [?]: [0], given: 1

Manager
Manager
User avatar
Joined: 23 Nov 2008
Posts: 78

Kudos [?]: 57 [0], given: 0

Re: Is 8 in S [#permalink]

Show Tags

New post 09 Dec 2008, 17:47
gutie859 wrote:
If the only member of S that is neither the square nor the cube of another member of S is called the source integer, is 8 in S?

If 64 is in and is not the source, then it is the square or a cube of a number in it. That would mean that 4 or 8 would have to be in. and if 4 is in and not the source , then wouldn't 2 have to be in too? So if 2 is in, 8 is in, and we needed to know that both 64 and 4 weren't the source...so the answer should be C



Statement 2 does not day anything about the number 4, so you cant assume its not the source.
Since statement 1 is already seen as sufficient, and 2 is not (given the info for 64), you dont need to consider option C..

Kudos [?]: 57 [0], given: 0

Intern
Intern
avatar
Joined: 01 Dec 2008
Posts: 27

Kudos [?]: [0], given: 1

Schools: Stern, Fuqua
Re: Is 8 in S [#permalink]

Show Tags

New post 09 Dec 2008, 17:59
ah good point, that was stupid of me..thanks

Kudos [?]: [0], given: 1

Re: Is 8 in S   [#permalink] 09 Dec 2008, 17:59
Display posts from previous: Sort by

S is a set of positive integers such that if integer x

  post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| 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®.