Last visit was: 25 Apr 2026, 15:53 It is currently 25 Apr 2026, 15:53
Home
Messages
Tests
Schools
Events
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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel
User avatar
MooseDrool
User avatar
Joined: 14 Jul 2006
Last visit: 21 Sep 2008
Posts: 4
Posts: 4
Kudos: 0
Is x^2 * y^2 an integer divisible by 9? 1) x is an integer 09 Aug 2007, 17:22
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Is x^2 * y^2 an integer divisible by 9?

1) x is an integer divisible by 3
2) x*y is an integer divisible by 9


Could someone please explain the fastest way to solve this problem?

I appreciate the help!



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
User avatar
bkk145
User avatar
Joined: 10 Jun 2007
Last visit: 23 Feb 2014
Posts: 645
Own Kudos:
1,801
Posts: 645
Kudos: 1,801
Is x^2 * y^2 an integer divisible by 9? 1) x is an integer 09 Aug 2007, 17:32
Kudos
Add Kudos
Bookmarks
Bookmark this Post
MooseDrool
Is x^2 * y^2 an integer divisible by 9?

1) x is an integer divisible by 3
2) x*y is an integer divisible by 9


Could someone please explain the fastest way to solve this problem?

I appreciate the help!
Show more


You get something like this: x^2 * y^2 = 3^2 * integer
Then you get: [(x*y) / 3]^2 = integer
This can only be true if x*y is divisible by 3.

1) INSUFFICIENT since y can be fraction
2) SUFFICIENT.
User avatar
MooseDrool
User avatar
Joined: 14 Jul 2006
Last visit: 21 Sep 2008
Posts: 4
Posts: 4
Kudos: 0
Is x^2 * y^2 an integer divisible by 9? 1) x is an integer 09 Aug 2007, 17:43
Kudos
Add Kudos
Bookmarks
Bookmark this Post
The answer was E. Your rationale looks right to me though.
User avatar
GK_Gmat
User avatar
Joined: 09 Aug 2006
Last visit: 28 Feb 2009
Posts: 348
Own Kudos:
1,078
Posts: 348
Kudos: 1,078
Is x^2 * y^2 an integer divisible by 9? 1) x is an integer 10 Aug 2007, 01:39
Kudos
Add Kudos
Bookmarks
Bookmark this Post
MooseDrool
Is x^2 * y^2 an integer divisible by 9?

1) x is an integer divisible by 3
2) x*y is an integer divisible by 9


Could someone please explain the fastest way to solve this problem?

I appreciate the help!
Show more


One more for B.

x^2*y^2= (xy)^2
Therefore, if xy is divisible by 9 then (xy)^2 has to be divisible by 9
User avatar
Fig
User avatar
Joined: 01 May 2006
Last visit: 02 Feb 2025
Posts: 1,031
Own Kudos:
253
Posts: 1,031
Kudos: 253
Is x^2 * y^2 an integer divisible by 9? 1) x is an integer 10 Aug 2007, 02:33
Kudos
Add Kudos
Bookmarks
Bookmark this Post
(B) for me :)

x^2 * y^2 = 9 * k ?

Stat 1
x = 3*j

2 cases:
o If y = 1/2 and x=3, then x^2 * y^2 = 9/4, which is not divisible by 9
o If y = 1 and x=3, then x^2 * y^2 = 9, which is divisible by 9

INSUFF.

Stat 2
x * y = 9 * v.....with v an integer
=> (x*y)^2 = 9 * 9 * v^2
<=> x^2 * y^2 = 9 * w....with w an integer such that w = 9 * v^2

SUFF.
User avatar
StartupAddict
User avatar
Joined: 31 Mar 2007
Last visit: 14 May 2009
Posts: 362
Own Kudos:
190
Location: Canada eh
Posts: 362
Kudos: 190
Is x^2 * y^2 an integer divisible by 9? 1) x is an integer 10 Aug 2007, 05:40
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Straight B. They say nothing about Y being an integer in A.

OA is B, not E.

A lot of those test writers know 0 about math, =P
User avatar
anonymousegmat
User avatar
Joined: 14 Jun 2007
Last visit: 14 Mar 2009
Posts: 300
Own Kudos:
29
Posts: 300
Kudos: 29
Is x^2 * y^2 an integer divisible by 9? 1) x is an integer 10 Aug 2007, 14:10
Kudos
Add Kudos
Bookmarks
Bookmark this Post
MooseDrool
Is x^2 * y^2 an integer divisible by 9?

1) x is an integer divisible by 3
2) x*y is an integer divisible by 9


Could someone please explain the fastest way to solve this problem?

I appreciate the help!
Show more


i am not looking at others explanations, i want to reason this on my own... so i might repeat others, i could be wrong.

I:

gut instinct is to pick A and move on... but we still need to know what Y is. y could be a fraction and then the answer could be no.

II: xy = 9*integer
theres lots of combinations that could yield a true statement here.

1*9
sqrt9*sqrt9
27* 1/3

all divisible by 9. I say B.
User avatar
anonymousegmat
User avatar
Joined: 14 Jun 2007
Last visit: 14 Mar 2009
Posts: 300
Own Kudos:
29
Posts: 300
Kudos: 29
Is x^2 * y^2 an integer divisible by 9? 1) x is an integer 10 Aug 2007, 14:12
Kudos
Add Kudos
Bookmarks
Bookmark this Post
MooseDrool
The answer was E. Your rationale looks right to me though.
Show more


???

how did they explain E as the answer, i am dying to know!

this is precisely why i asked for a refund for the challenges


:oops: :cry:



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!