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

It is currently 18 Oct 2018, 13:58

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

Is z + z < z ? (1) -4z > 4z (2) z^3 < z^2

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50000
Is z + z < z ? (1) -4z > 4z (2) z^3 < z^2  [#permalink]

Show Tags

New post 13 Mar 2018, 06:56
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

48% (01:28) correct 52% (01:38) wrong based on 43 sessions

HideShow timer Statistics

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50000
Re: Is z + z < z ? (1) -4z > 4z (2) z^3 < z^2  [#permalink]

Show Tags

New post 13 Mar 2018, 06:57
Bunuel wrote:
Is z + z < z ?

(1) -4z > 4z
(2) z^3 < z^2


9. Inequalities



For more check Ultimate GMAT Quantitative Megathread


_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

PS Forum Moderator
User avatar
P
Joined: 16 Sep 2016
Posts: 313
GMAT 1: 740 Q50 V40
GMAT ToolKit User Premium Member Reviews Badge CAT Tests
Re: Is z + z < z ? (1) -4z > 4z (2) z^3 < z^2  [#permalink]

Show Tags

New post 13 Mar 2018, 07:09
IMO A.

The question is asking if
2z < z

If we can certainly tell if z if either positive or negative we can answer the question.

St 1 : -4z > 4z
This is only true for z < 0.
Hence suff.

St 2 : z^3 < z^2

Two possibilities :

1) z could be negative
Hence z^3 ( neg no.) < z^2 ( positive no.)

2) z could be positive and less than 1.

Z^3 < z^2 still holds.

Not sufficient .

Hence A.

Posted from my mobile device
VP
VP
User avatar
V
Status: It's near - I can see.
Joined: 13 Apr 2013
Posts: 1267
Location: India
Concentration: International Business, Operations
GMAT 1: 480 Q38 V22
GPA: 3.01
WE: Engineering (Consulting)
Premium Member Reviews Badge CAT Tests
Is z + z < z ? (1) -4z > 4z (2) z^3 < z^2  [#permalink]

Show Tags

New post 13 Mar 2018, 10:10
1
Bunuel wrote:
Is z + z < z ?

(1) -4z > 4z
(2) z^3 < z^2


Question: Is \(z + z < z ?\)

or Is \(2z - z < 0 ?\)

or Is \(z < 0 ?\)

St 1:\(- 4z > 4z\)

or \(8z < 0\)

or \(z < 0\) Sufficient

St 2 : \(z^3 < z^2\)

or \(z^3 - z^2 < 0\)

or \(z^2 ( z - 1) < 0\)

\(z^2 > 0\) for \(z < 0\) or \(z > 0\)

\(z - 1 < 0\)

\(z < 1\)

Therefore combined range is \(z < 0\) or \(0 < z < 1.\) Not sufficient

(A)
_________________

"Do not watch clock; Do what it does. KEEP GOING."

RC Moderator
User avatar
P
Joined: 24 Aug 2016
Posts: 401
Location: Canada
Concentration: Entrepreneurship, Operations
GMAT 1: 630 Q48 V28
GMAT ToolKit User Reviews Badge CAT Tests
Re: Is z + z < z ? (1) -4z > 4z (2) z^3 < z^2  [#permalink]

Show Tags

New post 13 Mar 2018, 10:29
1. -4z>4z => z is +ve hence 2z>z ---->S
2. z^3 <z^2 => z is -ve or 0<z<1
if z is -ve => 2z<z ---->S
but if z is -ve or 0<z<1 =>2z>z ---->NS Thus 2. is NS

Hence I would go for option A.
_________________

Please let me know if I am going in wrong direction.
Thanks in appreciation.

Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 6385
GMAT 1: 760 Q51 V42
GPA: 3.82
Premium Member
Re: Is z + z < z ? (1) -4z > 4z (2) z^3 < z^2  [#permalink]

Show Tags

New post 15 Mar 2018, 13:03
Bunuel wrote:
Is z + z < z ?

(1) -4z > 4z
(2) z^3 < z^2


Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.

The first step of the VA (Variable Approach) method is to modify the original condition and the question. We then recheck the question.

The question is modified as follows.
2z < z ?
⇔ z < 0 ?

Condition 1)
-4z > 4z
⇔ 0 > 8z
⇔ 0 > z
It is same as the question.
Condition 1) is sufficient.

Condition 2)
z^3 < z^2
⇔ z^3 - z^2 < 0
⇔ z^2(z-1) < 0
⇔ z - 1 < 0 since z^2 > 0
⇔ z < 1
Since the range of the question does not include that of the condition 2), the condition 2) is not sufficient.

Therefore, the answer is A.
_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $99 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

SVP
SVP
User avatar
D
Joined: 26 Mar 2013
Posts: 1836
Reviews Badge CAT Tests
Re: Is z + z < z ? (1) -4z > 4z (2) z^3 < z^2  [#permalink]

Show Tags

New post 15 Mar 2018, 13:10
Bunuel wrote:
Is z + z < z ?

(1) -4z > 4z
(2) z^3 < z^2



Rephrase the question:

Is z <0??

(1) -4z > 4z

8z < 0....Z must be negative...........Answer is always Yes.

Sufficient

(2) z^3 < z^2

Let x = 1/2 ............1/8 < 1/4 ..........Answer is NO
Let x =-1/2 .......... -1/8 < 1/4 ..........Answer is Yes

Insufficient

Answer: A
GMAT Club Bot
Re: Is z + z < z ? (1) -4z > 4z (2) z^3 < z^2 &nbs [#permalink] 15 Mar 2018, 13:10
Display posts from previous: Sort by

Is z + z < z ? (1) -4z > 4z (2) z^3 < z^2

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


Copyright

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