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

It is currently 16 Oct 2019, 15:03

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

M28-46

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

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 58381
M28-46  [#permalink]

Show Tags

New post 16 Sep 2014, 01:31
1
4
00:00
A
B
C
D
E

Difficulty:

  95% (hard)

Question Stats:

37% (00:54) correct 63% (00:57) wrong based on 251 sessions

HideShow timer Statistics

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 58381
Re M28-46  [#permalink]

Show Tags

New post 16 Sep 2014, 01:31
2
Official Solution:


Is \(x(x-2) \gt 0\)?

Is \(x \lt 0\) or \(x \gt 2\). Basically if \(x\) is not 0, 1, or 2 we have an YES answer to the question.

(1) \(x\) is a prime number. If \(x=2\) then the answer is NO but if \(x\) is some other prime, then the answer is YES. Not sufficient.

(2) \(x^2\) is a multiple of 9. If \(x=0\) then the answer is NO but if \(x=3\), then the answer is YES. Not sufficient.

(1)+(2) Since from (1) \(x\) is a prime and from (2) \(x^2\) is a multiple of 9, then \(x\) can only be 3. Therefore the answer to the question is YES. Sufficient.


Answer: C
_________________
Intern
Intern
avatar
Joined: 06 Oct 2010
Posts: 6
Location: Bangalore
Reviews Badge
Re: M28-46  [#permalink]

Show Tags

New post 26 Dec 2014, 05:20
Bunuel wrote:
Official Solution:


Is \(x(x-2) \gt 0\)?

Is \(x \lt 0\) or \(x \gt 2\). Basically if \(x\) is not 0, 1, or 2 we have an YES answer to the question.

(1) \(x\) is a prime number. If \(x=2\) then the answer is NO but if \(x\) is some other prime, then the answer is YES. Not sufficient.

(2) \(x^2\) is a multiple of 9. If \(x=0\) then the answer is NO but if \(x=3\), then the answer is YES. Not sufficient.

(1)+(2) Since from (1) \(x\) is a prime and from (2) \(x^2\) is a multiple of 9, then \(x\) can only be 3. Therefore the answer to the question is YES. Sufficient.


Answer: C


Hi Bunuel,

If X^2 is a multiple of 9,how can we say x can have a value of zero? Please clarify.
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 58381
Re: M28-46  [#permalink]

Show Tags

New post 26 Dec 2014, 08:03
royinkol wrote:
Bunuel wrote:
Official Solution:


Is \(x(x-2) \gt 0\)?

Is \(x \lt 0\) or \(x \gt 2\). Basically if \(x\) is not 0, 1, or 2 we have an YES answer to the question.

(1) \(x\) is a prime number. If \(x=2\) then the answer is NO but if \(x\) is some other prime, then the answer is YES. Not sufficient.

(2) \(x^2\) is a multiple of 9. If \(x=0\) then the answer is NO but if \(x=3\), then the answer is YES. Not sufficient.

(1)+(2) Since from (1) \(x\) is a prime and from (2) \(x^2\) is a multiple of 9, then \(x\) can only be 3. Therefore the answer to the question is YES. Sufficient.


Answer: C


Hi Bunuel,

If X^2 is a multiple of 9,how can we say x can have a value of zero? Please clarify.


0 is divisible by EVERY integer except 0 itself, because 0/integer = 0 = integer.
_________________
Intern
Intern
avatar
Joined: 13 Oct 2012
Posts: 11
Schools: Foster '18
GMAT 1: 560 Q42 V24
Reviews Badge
Re: M28-46  [#permalink]

Show Tags

New post 21 Oct 2015, 14:40
Hi Bunuel,

Can we consider Is x2>2x? as 'IS X>2'?

Thanks.
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 58381
Re: M28-46  [#permalink]

Show Tags

New post 21 Oct 2015, 21:08
patilvrishali101 wrote:
Hi Bunuel,

Can we consider Is x2>2x? as 'IS X>2'?

Thanks.


No. We cannot reduce an equation by a variable if we don't know its sign: if x is positive, then yes, from x^2 > 2x we get x > 2 BUT if x is negative, then when reducing by negative value we must flip the sign and we'd get x < 2.

For more check below links:

Inequalities Made Easy!

Solving Quadratic Inequalities - Graphic Approach
Inequality tips

DS Inequalities Problems
PS Inequalities Problems

700+ Inequalities problems

inequalities-trick-91482.html
data-suff-inequalities-109078.html
range-for-variable-x-in-a-given-inequality-109468.html
everything-is-less-than-zero-108884.html
graphic-approach-to-problems-with-inequalities-68037.html
_________________
Intern
Intern
avatar
Joined: 04 Sep 2015
Posts: 6
Re: M28-46  [#permalink]

Show Tags

New post 14 Feb 2016, 05:06
Hi Bunuel,

could you elaborate why x<0? How did you come to that? I do understand that x-2>0 equals x>2.

Thx.
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 58381
Re: M28-46  [#permalink]

Show Tags

New post 14 Feb 2016, 05:11
Current Student
User avatar
D
Joined: 12 Aug 2015
Posts: 2568
Schools: Boston U '20 (M)
GRE 1: Q169 V154
GMAT ToolKit User
Re: M28-46  [#permalink]

Show Tags

New post 09 Mar 2016, 00:40
Excellent Question ..
here i was tempted to choose A and B but here is why i chose C
here in statement 1 => x can be 2
in statement 2 x can be 0 too as 0 is the multiple of every number .
Hence C
_________________
Manager
Manager
User avatar
Joined: 15 May 2010
Posts: 147
Location: India
Concentration: Strategy, General Management
WE: Engineering (Manufacturing)
Reviews Badge
Re: M28-46  [#permalink]

Show Tags

New post 07 Apr 2016, 02:35
Bunnel

Here, in option 1):- x is prime number, which is always positive one, so we ignored X<0 .

Only we checked the condition x>2

Am I right?


Bunuel wrote:
Official Solution:


Is \(x(x-2) \gt 0\)?

Is \(x \lt 0\) or \(x \gt 2\). Basically if \(x\) is not 0, 1, or 2 we have an YES answer to the question.

(1) \(x\) is a prime number. If \(x=2\) then the answer is NO but if \(x\) is some other prime, then the answer is YES. Not sufficient.

(2) \(x^2\) is a multiple of 9. If \(x=0\) then the answer is NO but if \(x=3\), then the answer is YES. Not sufficient.

(1)+(2) Since from (1) \(x\) is a prime and from (2) \(x^2\) is a multiple of 9, then \(x\) can only be 3. Therefore the answer to the question is YES. Sufficient.


Answer: C
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 58381
Re: M28-46  [#permalink]

Show Tags

New post 07 Apr 2016, 08:30
sun01 wrote:
Bunnel

Here, in option 1):- x is prime number, which is always positive one, so we ignored X<0 .

Only we checked the condition x>2

Am I right?


Bunuel wrote:
Official Solution:


Is \(x(x-2) \gt 0\)?

Is \(x \lt 0\) or \(x \gt 2\). Basically if \(x\) is not 0, 1, or 2 we have an YES answer to the question.

(1) \(x\) is a prime number. If \(x=2\) then the answer is NO but if \(x\) is some other prime, then the answer is YES. Not sufficient.

(2) \(x^2\) is a multiple of 9. If \(x=0\) then the answer is NO but if \(x=3\), then the answer is YES. Not sufficient.

(1)+(2) Since from (1) \(x\) is a prime and from (2) \(x^2\) is a multiple of 9, then \(x\) can only be 3. Therefore the answer to the question is YES. Sufficient.


Answer: C


Yes, only positive integers can be primes, if that's what you mean.
_________________
Retired Moderator
avatar
B
Status: I Declare War!!!
Joined: 02 Apr 2014
Posts: 231
Location: United States
Concentration: Finance, Economics
GMAT Date: 03-18-2015
WE: Asset Management (Investment Banking)
GMAT ToolKit User
Re: M28-46  [#permalink]

Show Tags

New post 24 Jul 2016, 19:20
Hi!
A small doubt..
x(x-2)>0
x>2 and x,0...
but is it not x>2 and x> 0?
why inequity sign changed in second while comparing to zero?
thanks
any imp theory link you like to share please...
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 58381
Re: M28-46  [#permalink]

Show Tags

New post 24 Jul 2016, 21:57
SVP
SVP
User avatar
V
Joined: 26 Mar 2013
Posts: 2347
Reviews Badge CAT Tests
M28-46  [#permalink]

Show Tags

New post 25 Jul 2016, 03:25
3
Celestial09 wrote:
Hi!
A small doubt..
x(x-2)>0
x>2 and x,0...
but is it not x>2 and x> 0?
why inequity sign changed in second while comparing to zero?
thanks
any imp theory link you like to share please...



I'm happy to answer your doubt, regardless of the question. I will answer it as we solve inequality.

What does it mean X(X-2)>0 ? Let's put it in simple way.

We have TWO number A & B are multiplied and result Bigger than 0. When does Happen?

From NUMBER PROPERTIES:

Case 1: A = positive & B= positive ............ A * B >0

Case 2: A =negative & B= negative ............ A * B >0

Let look to our inequality :

X(X-2)>0

Put: A=X & B= X-2

Using cases mentioned above let's analyze our inequality:

Case 1:

X (X-2)>0.......... Remember A & B positive means A >0 & B>0

X>0 & X-2>0 then X>2 ....... Can you come up with example that satisfy that X>0 & X>2 in same time???Answer:YES we can. Any number BIGGER than 2 does so

CASE 1 yields that X>2

Case 2

X (X-2)>0.......... Remember A & B negative means A <0 & B<0

X<0 & X-2<0 then X<2........Can you come up with example that satisfy that X<0 & X<2 in same time???Answer:YES we can. Any number SMALLER than 0 does so.

CASE 2 yields that X<0

From above Cases we can conclude FINALLY that: TO SATISFY the Inequality:

Either X<0 or X>2................NOTICE that when we combine TWO CASES, we use 'Either......OR......'

You can check number if you are in doubt.

I will expand my explanation about how to solve if you face this question:

X (X-2)<0

From NUMBER PROPERTIES:

Case 1: A = positive & B= negative ............ A * B <0

Case 2: A =negative & B= positive ............ A * B <0

Put: A=X & B= X-2

Using cases mentioned above let's analyze our inequality:

Case 1:

X (X-2)<0.......... Remember A = positive means A >0 & B=negative means B<0

X>0 & X-2<0 then X<2 ....... Can you come up with example that satisfy that X>0 & X<2 in same time???Answer:YES we can. Any number BIGGER than 0
& SMALLER than 2. We can put mathematically as 0<X<2. For example X=3/2

CASE 1 yields that 0<X<2


Case 2

X (X-2)>0.......... Remember A = negative means A < 0 & B=positive means B>0

X<0 & X-2>0 then X>2........Can you come up with example that satisfy that X<0 & X>2 in same time???Answer:NO, we can NOT. It means that we need a number that is negative and positive in same time. Can you find it? :)

CASE 2 yields no solution


From above Cases we can conclude FINALLY that: TO SATISFY the Inequality:

0<X<2

Check numbers if you want.
VP
VP
User avatar
P
Joined: 14 Feb 2017
Posts: 1186
Location: Australia
Concentration: Technology, Strategy
Schools: LBS '22
GMAT 1: 560 Q41 V26
GMAT 2: 550 Q43 V23
GMAT 3: 650 Q47 V33
GMAT 4: 650 Q44 V36
WE: Management Consulting (Consulting)
Reviews Badge CAT Tests
Re: M28-46  [#permalink]

Show Tags

New post 11 Dec 2018, 14:45
This came up my email from the QOTD.

I said (b), but stupidly didn't consider x=0
_________________
Goal: Q49, V41

+1 Kudos if I have helped you
Senior Manager
Senior Manager
User avatar
G
Joined: 13 Feb 2018
Posts: 450
GMAT 1: 640 Q48 V28
Premium Member
Re: M28-46  [#permalink]

Show Tags

New post 23 Jan 2019, 06:12
After 1 minute i was about to smash B, but then I spent another 45 secs to arrive at a correct answer.

The difficulty level indicator plays a good role while solving such questions

Wish at real GMAT exam we had such priceless tiny indicator


Regards
L
GMAT Club Bot
Re: M28-46   [#permalink] 23 Jan 2019, 06:12
Display posts from previous: Sort by

M28-46

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

Moderators: chetan2u, Bunuel






Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne