GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 17 Aug 2018, 10:07

### 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

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

# If x2/9 4/y2 = 12, what is the value of x? (1) x/3 + 2/y = 6

Author Message
Senior Manager
Joined: 19 Mar 2008
Posts: 344
If x2/9 4/y2 = 12, what is the value of x? (1) x/3 + 2/y = 6  [#permalink]

### Show Tags

26 Jul 2008, 00:46
00:00

Difficulty:

(N/A)

Question Stats:

100% (04:33) correct 0% (00:00) wrong based on 1 sessions

### HideShow timer Statistics

If x2/9 – 4/y2 = 12, what is the value of x?

(1) x/3 + 2/y = 6

(2) x/3 – 2/y = 2

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Director
Joined: 10 Sep 2007
Posts: 909
Re: DS: value of x (n3.17)  [#permalink]

### Show Tags

Updated on: 26 Jul 2008, 11:14
IMO D.

2 equations 2 variable (1 equation from question and one from statement).

From 1 the equation 4/y^2 = 36+x^2/9-4x
From 2 the equation 4/y^2 = 4+X^2/9+4x/3

Originally posted by abhijit_sen on 26 Jul 2008, 09:03.
Last edited by abhijit_sen on 26 Jul 2008, 11:14, edited 1 time in total.
VP
Joined: 28 Dec 2005
Posts: 1477
Re: DS: value of x (n3.17)  [#permalink]

### Show Tags

26 Jul 2008, 09:20
same reasoning as above for D . Two eqns, two unknowns, so each statement on its own should be sufficient ... dont have to bother to solve
Senior Manager
Joined: 19 Mar 2008
Posts: 344
Re: DS: value of x (n3.17)  [#permalink]

### Show Tags

26 Jul 2008, 10:18
Good explanation.

OA is D
Director
Joined: 10 Sep 2007
Posts: 909
Re: DS: value of x (n3.17)  [#permalink]

### Show Tags

26 Jul 2008, 11:01
1
pmenon wrote:
same reasoning as above for D . Two eqns, two unknowns, so each statement on its own should be sufficient ... dont have to bother to solve

please note that I also did not solve to the end. But we do need to solve it till the point I solved. Because it might happen that we end up in a quadratic equation in X, which might give you 2 value in which case A alone or B alone may not be sufficient and we may have to go for combined value.
Senior Manager
Joined: 23 May 2006
Posts: 298
Re: DS: value of x (n3.17)  [#permalink]

### Show Tags

26 Jul 2008, 11:17
Good explanation Abhijit.

Kudos for you.
Senior Manager
Joined: 19 Mar 2008
Posts: 344
Re: DS: value of x (n3.17)  [#permalink]

### Show Tags

26 Jul 2008, 23:29
abhijit_sen wrote:
pmenon wrote:
same reasoning as above for D . Two eqns, two unknowns, so each statement on its own should be sufficient ... dont have to bother to solve

please note that I also did not solve to the end. But we do need to solve it till the point I solved. Because it might happen that we end up in a quadratic equation in X, which might give you 2 value in which case A alone or B alone may not be sufficient and we may have to go for combined value.

well said. abhijit.

In exam, if I have time, I will make sure I solve to the end.
Intern
Joined: 15 Jul 2008
Posts: 42
Re: DS: value of x (n3.17)  [#permalink]

### Show Tags

29 Jul 2008, 02:19
abhijit_sen wrote:
IMO D.

2 equations 2 variable (1 equation from question and one from statement).

From 1 the equation 4/y^2 = 36+x^2/9-4x
From 2 the equation 4/y^2 = 4+X^2/9+4x/3

in exam if I have no time to solve to the end, what are signals to recognize the suff anwer. As you mentioned above, 2 equations 2 variable, but one is a line, one is a quadratic equation, so they can cut each other at 2 points so we have 2 value, or 1 point or no point. So it it hard to pick the answer if we don't solve to the end.
VP
Joined: 17 Jun 2008
Posts: 1474
Re: DS: value of x (n3.17)  [#permalink]

### Show Tags

29 Jul 2008, 02:50
The way I would solve this is as below.

x^2/9 - 4/y^2 = 12 or (x/3+2/y)(x/3-2/y) = 12

Stmt 1: if x/3 + 2/y is 6 then x/3-2/y will become 2.

We can add the two equations and get 2x/3 = 8 or x = 12.

Similarly, Stmt2.

Senior Manager
Joined: 19 Mar 2008
Posts: 344
Re: DS: value of x (n3.17)  [#permalink]

### Show Tags

29 Jul 2008, 07:00
scthakur wrote:
The way I would solve this is as below.

x^2/9 - 4/y^2 = 12 or (x/3+2/y)(x/3-2/y) = 12

Stmt 1: if x/3 + 2/y is 6 then x/3-2/y will become 2.

We can add the two equations and get 2x/3 = 8 or x = 12.

Similarly, Stmt2.

can you elaborate this "We can add the two equations and get 2x/3 = 8 or x = 12."?
SVP
Joined: 07 Nov 2007
Posts: 1728
Location: New York
Re: DS: value of x (n3.17)  [#permalink]

### Show Tags

30 Jul 2008, 13:41
judokan wrote:
If x2/9 – 4/y2 = 12, what is the value of x?

(1) x/3 + 2/y = 6

(2) x/3 – 2/y = 2

x2/9 – 4/y2 = 12 -->
(x/3+2/y)(x/3 - 2/y)=12 --(equation A)

(1) x/3 + 2/y = 6 -----(equation B)
substitute (1) above value into equation (A)
(x/3+2/y)(x/3 - 2/y)=12 --> 6 (x/3 - 2/y)=12
--> x/3 - 2/y =2 --- (equation C)
we have two equations.. two unknowns... must be sufficient
(2) x/3 – 2/y = 2 -- (C)
(x/3+2/y)2=12 --> 2 (x/3 - 2/y)=6
we have two equations.. two unknowns... must be sufficient

Did you observe that State1 * State 2 = Question..---> then we can say that Answer D...(when State1 & State2 are not quartic/cubic.. higher power.. have only two unknown variables.)
No calculations..required..
_________________

Smiling wins more friends than frowning

VP
Joined: 17 Jun 2008
Posts: 1279
Re: DS: value of x (n3.17)  [#permalink]

### Show Tags

03 Aug 2008, 08:46
judokan wrote:
If x2/9 – 4/y2 = 12, what is the value of x?

(1) x/3 + 2/y = 6

(2) x/3 – 2/y = 2

IMO D

since given that :
(x/3 + 2/y)(x/3 – 2/y)=12

(1) says x/3 + 2/y = 6
=> (x/3 – 2/y)=12/6=2 => combining these two x=12 SUFF

(2) says x/3 – 2/y = 2
=> x/3 + 2/y = 6 => combining these two x=12 SUFF

IMO D

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.

_________________

cheers
Its Now Or Never

Re: DS: value of x (n3.17) &nbs [#permalink] 03 Aug 2008, 08:46
Display posts from previous: Sort by

# Events & Promotions

 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®.