It is currently 17 Oct 2017, 01:06

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

ps:m24 #21

  post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Manager
Manager
User avatar
Joined: 05 Jan 2009
Posts: 81

Kudos [?]: 160 [0], given: 2

ps:m24 #21 [#permalink]

Show Tags

New post 25 Jul 2009, 14:14
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

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

HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

How to solve it?
GMATclub test24
Attachments

m24.JPG
m24.JPG [ 39.5 KiB | Viewed 1296 times ]

Kudos [?]: 160 [0], given: 2

Senior Manager
Senior Manager
avatar
Joined: 25 Jun 2009
Posts: 298

Kudos [?]: 150 [0], given: 6

Re: ps:m24 #21 [#permalink]

Show Tags

New post 25 Jul 2009, 14:50
pmal04 wrote:
How to solve it?
GMATclub test24



IMO its should be C. These are equations for parabola, now trying substituting diff values of 'a' and try to make a figure out of it ( if a= +ve then you will get a figure some thing like this which is attached and if a=-ve then its mirror image)

I hope this helped else let me know I will elaborate.
Please confirm answer as well.

Cheers
Attachments

untitled.JPG
untitled.JPG [ 7.66 KiB | Viewed 1275 times ]

Kudos [?]: 150 [0], given: 6

Expert Post
GMAT Tutor
avatar
B
Joined: 24 Jun 2008
Posts: 1339

Kudos [?]: 1951 [0], given: 6

Re: ps:m24 #21 [#permalink]

Show Tags

New post 26 Jul 2009, 08:16
Recall how we find intersection points - we just solve the two equations together. So really you're just trying to determine if ax^2 + b = cx^2 + d has any solutions, or equivalently, if (a - c)x^2 = d - b has any solutions, or perhaps most simply, if x^2 = (d-b)/(a-c) has any solutions. If the right side of this equation is zero or positive, we'll be able to find one or two values of x, respectively. If the right side is negative, there will be no solutions. So we can rephrase the question: is (d-b)/(a-c) > 0?

Since we need to know about both the numerator and denominator of (d-b)/(a-c), neither statement is sufficient alone. Combining the statements, since c = -a, our fraction becomes (d-b)/(2a). From Statement 2, d-b is negative. Still, we don't know if a is positive or negative; if a is positive, the fraction is negative, and if a is negative, the fraction is positive. Insufficient.

Of course, if you recognize that these are equations of parabolas, you can use coordinate geometry principles to solve. S1 tells us that one parabola is rising, one falling. Statement 2 tells us that the first parabola has a higher vertex than the second. Still, we have two possibilities; if the first parabola is rising, and the second falling, they don't intersect. If the first parabola is falling and the second rising, they do. Insufficient.

All that said, the wording of the question is very bad - the equations in the question clearly do not define 'lines'; they define 'curves'.
_________________

GMAT Tutor in Toronto

If you are looking for online GMAT math tutoring, or if you are interested in buying my advanced Quant books and problem sets, please contact me at ianstewartgmat at gmail.com

Kudos [?]: 1951 [0], given: 6

Director
Director
avatar
Joined: 05 Jun 2009
Posts: 810

Kudos [?]: 373 [0], given: 106

WE 1: 7years (Financial Services - Consultant, BA)
Re: ps:m24 #21 [#permalink]

Show Tags

New post 27 Jul 2009, 05:38
nitishmahajan wrote:
pmal04 wrote:
How to solve it?
GMATclub test24



IMO its should be C. These are equations for parabola, now trying substituting diff values of 'a' and try to make a figure out of it ( if a= +ve then you will get a figure some thing like this which is attached and if a=-ve then its mirror image)

I hope this helped else let me know I will elaborate.
Please confirm answer as well.

Cheers


HI Nitish,

Right approach, but I think you missed the point when a is negative, it'll not be mirror image, but there will be two intersection(because Y intercepts didn't change)

So, correct answer is E.
_________________

Consider kudos for the good post ... :beer
My debrief : http://gmatclub.com/forum/journey-670-to-720-q50-v36-long-85083.html

Kudos [?]: 373 [0], given: 106

Senior Manager
Senior Manager
avatar
Joined: 25 Jun 2009
Posts: 298

Kudos [?]: 150 [0], given: 6

Re: ps:m24 #21 [#permalink]

Show Tags

New post 27 Jul 2009, 05:51
sudeep wrote:
nitishmahajan wrote:
pmal04 wrote:
How to solve it?
GMATclub test24



IMO its should be C. These are equations for parabola, now trying substituting diff values of 'a' and try to make a figure out of it ( if a= +ve then you will get a figure some thing like this which is attached and if a=-ve then its mirror image)

I hope this helped else let me know I will elaborate.
Please confirm answer as well.

Cheers


HI Nitish,

Right approach, but I think you missed the point when a is negative, it'll not be mirror image, but there will be two intersection(because Y intercepts didn't change)

So, correct answer is E.



Hi Sudeep,

I agree that when a is -ve it wont be the mirror image but I guess in that case also it won't intersect as d< b. So, I think the figure would be some thing like this. In this case the second parabola will be inside the first parabola but I think it won't intersect.

Cheers
Attachments

untitled.JPG
untitled.JPG [ 8.86 KiB | Viewed 1228 times ]

Kudos [?]: 150 [0], given: 6

Director
Director
avatar
Joined: 05 Jun 2009
Posts: 810

Kudos [?]: 373 [0], given: 106

WE 1: 7years (Financial Services - Consultant, BA)
Re: ps:m24 #21 [#permalink]

Show Tags

New post 27 Jul 2009, 06:56
Nitish,

See this:
Attachments

quad1.jpg
quad1.jpg [ 19.16 KiB | Viewed 1219 times ]


_________________

Consider kudos for the good post ... :beer
My debrief : http://gmatclub.com/forum/journey-670-to-720-q50-v36-long-85083.html

Kudos [?]: 373 [0], given: 106

Senior Manager
Senior Manager
avatar
Joined: 25 Jun 2009
Posts: 298

Kudos [?]: 150 [0], given: 6

Re: ps:m24 #21 [#permalink]

Show Tags

New post 27 Jul 2009, 10:13
sudeep wrote:
Nitish,

See this:


Thanks Sudeep, I got it now :)

Kudos [?]: 150 [0], given: 6

Re: ps:m24 #21   [#permalink] 27 Jul 2009, 10:13
Display posts from previous: Sort by

ps:m24 #21

  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®.