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

It is currently 19 Apr 2014, 22:00

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

OG DS Question - Disagree with OE

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 07 Jul 2004
Posts: 5099
Location: Singapore
Followers: 15

Kudos [?]: 120 [0], given: 0

GMAT Tests User
OG DS Question - Disagree with OE [#permalink] New post 03 Sep 2004, 10:18
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
Hi,

Went through this OG question for DS. Didn't quite agree with the explanation. Wonder if anyone has a better idea.

If x+y+z > 0, is z > 1?

1) z > x+ y+ 1
2) x+ y+ 1 < 0

I'll post the OE after some discussion.
Intern
Intern
Joined: 10 Aug 2004
Posts: 40
Followers: 0

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

 [#permalink] New post 03 Sep 2004, 10:49
B is sufficient because if X+Y<-1 then Z must be more that 1 in order for X+Y+Z to be more than 1. My impression is that A is correct as well, but I think it might be a trap answer. So I will guess is D but i have feeling I am making a mistake.
Manager
Manager
Joined: 02 Apr 2004
Posts: 224
Location: Utrecht
Followers: 1

Kudos [?]: 4 [0], given: 0

GMAT Tests User
 [#permalink] New post 03 Sep 2004, 11:00
Yeah, I also came to choice D

st 1.
I didn't use numbers but:
z > x + y + 1
z - x - y > 1

x + y + z > 0
z > -x - y

st 2.
I used numbers and came to all that z > 1

I am honest, and did not look that careful to this question.
(6 hours GMAT today cant be that healthy...time for a break)

Please correct me if I am wrong.

Regards,

Alex
GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 07 Jul 2004
Posts: 5099
Location: Singapore
Followers: 15

Kudos [?]: 120 [0], given: 0

GMAT Tests User
 [#permalink] New post 03 Sep 2004, 11:10
Here's what the OE did, which I wasn't entirely convinced.

For statement 1: z > x+y+1

It says statement 1 is not sufficient. What it did was to use x + y + z > 0, so x+y > -z, so that using (1), z > x+y+1>-z+1, impllies z > 0.5. What happens here is it took x+y to be equal to -z and substituted it inside the inequality. But x+y is not equals -z, it is greater than -z. So x+y can be anything, say, -z+1, or -z+20 etc. So if x+y=-z+20, then z > -z+20+1, 2z > 21, z > 21/2 !

For statement 2: x+y<-1, so z>1 for x+y+z>0.

What do you think of the OE for statement (1) ?
Intern
Intern
Joined: 02 Sep 2004
Posts: 35
Followers: 0

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

OG is right [#permalink] New post 03 Sep 2004, 12:05
Statement 1 is insufficient while statement 2 is sufficient.
1) is insufficient cause -
We have x + y + z > 0 given and by 1) z> x + y + 1.

Take x = -.75, y = 0.25 and z = 0.75. We satisfy both the equations.
Yet z<1.
Take x = 1, y = 1 and z =4. We again satisy both equations but z>1

So insufficient.

Mathematical proof.
Add both inequatities - Addition does not change signs.
we get x + y + 2z > x + y + 1
Which is 2z > 1 or z > 1/2

Thus if the question were - is z > 1/2 then answer would be D.
Hope this ends the debate....
_________________

To be or not to be....

Director
Director
User avatar
Joined: 31 Aug 2004
Posts: 611
Followers: 2

Kudos [?]: 12 [0], given: 0

GMAT Tests User
 [#permalink] New post 03 Sep 2004, 14:40
My 1st draft :

1) x+y+z>0 & z>x+y+1

id est 2z>x+y+z+1>1 which means that z>1/2 No

2) x+y+z>0 <=> x+y>-z

id est -z+1 <x+y+1<0 => z>1 OK

I would choose answer B
  [#permalink] 03 Sep 2004, 14:40
    Similar topics Author Replies Last post
Similar
Topics:
New posts OG DS Line equation question ugo_castelo 7 27 Sep 2006, 10:48
New posts Green OG (quant review) DS question hsk 1 07 Jun 2007, 22:37
New posts OG 12, DS question 166 gmattester123 2 06 Sep 2009, 20:56
This topic is locked, you cannot edit posts or make further replies. New DS question OG 10 pranrasvij 1 17 Jun 2010, 11:27
New posts 1 OG Critical Reasoning #1 - I disagree? Gottesschaf 4 12 Jan 2011, 12:03
Display posts from previous: Sort by

OG DS Question - Disagree with OE

  Question banks Downloads My Bookmarks Reviews Important topics  


cron

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®.