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

 It is currently 30 Apr 2016, 19:23

### 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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# m04 Q23

Author Message
Manager
Joined: 20 Mar 2008
Posts: 159
Location: USA
Followers: 2

Kudos [?]: 34 [0], given: 0

### Show Tags

14 Sep 2008, 06:12
Is integer $$Z$$ odd?

1. $$\frac{Z}{3}$$ is odd
2. $$3Z$$ is odd

[Reveal] Spoiler: OA
D

Source: GMAT Club Tests - hardest GMAT questions

Here OA is D with explanation S2 also implies that $$Z$$ is odd.

Why can't S2 be a fraction? For example 5/3.

I think answer to this question needs to be changed.
SVP
Joined: 30 Apr 2008
Posts: 1888
Location: Oklahoma City
Schools: Hard Knocks
Followers: 39

Kudos [?]: 517 [0], given: 32

### Show Tags

14 Sep 2008, 06:48
I'm not sure why you're saying "Why can't statement 2 be a fraction?" when the question stem says "integer Z".

if $$\frac{Z}{3}$$ is odd, then this means the result is an integer because decimials are neither even nor odd. If we take values for Z that when divided by 3 give us integers, we can use (3, 6, 9, 12, 15, 18, 21...}

The resulting value when each is divided by 3 is {1, 2, 3, 4, 5, 6, 7...}. Lets look at which values for Z give us the odd value...that would be 3, 9, 15, 21..etc. These are also odd. So Z is odd from statement 1.

With statement 2, we have to remember number properties. Odd * Odd = Odd [always!]. So if 3*Z is odd, Z must be odd. Just as simple as that.

vishy007 wrote:
Is integer $$Z$$ odd?

1. $$\frac{Z}{3}$$ is odd
2. $$3Z$$ is odd

Here OA is D with explanation S2 also implies that $$Z$$ is odd.

Why can't S2 be a fraction? For example 5/3.

I think answer to this question needs to be changed.

_________________

------------------------------------
J Allen Morris
**I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a.

GMAT Club Premium Membership - big benefits and savings

Math Expert
Joined: 02 Sep 2009
Posts: 32549
Followers: 5632

Kudos [?]: 68314 [3] , given: 9797

### Show Tags

18 Oct 2012, 05:18
3
KUDOS
Expert's post
vishy007 wrote:
Is integer $$Z$$ odd?

1. $$\frac{Z}{3}$$ is odd
2. $$3Z$$ is odd

[Reveal] Spoiler: OA
D

Source: GMAT Club Tests - hardest GMAT questions

Here OA is D with explanation S2 also implies that $$Z$$ is odd.

Why can't S2 be a fraction? For example 5/3.

I think answer to this question needs to be changed.

Is integer $$z$$ odd?

(1) $$\frac{z}{3}$$ is odd --> $$\frac{z}{3}=odd$$ --> $$z=3*odd=odd$$. Sufficient.

(2) $$3z$$ is odd --> $$3z=odd$$ --> in order the product of two integers 3 and $$z$$ to be odd both must be odd. So, $$z=odd$$. Sufficient.

_________________
Manager
Joined: 20 Jun 2008
Posts: 53
Followers: 0

Kudos [?]: 12 [0], given: 1

### Show Tags

18 Oct 2012, 05:23
The email that comes as GMAT question of the day, says -- 2. 49 is odd. This seemed odd, but looking at the actuals question on this webpage makes it clear about answer being D.
Director
Status: Final Countdown
Joined: 17 Mar 2010
Posts: 563
Location: India
GPA: 3.82
WE: Account Management (Retail Banking)
Followers: 16

Kudos [?]: 224 [0], given: 75

### Show Tags

18 Oct 2012, 05:30
(i) z/3=odd
z=oddx3
z=oddXodd
always odd-sufficient

(ii) 3z=odd
if z is odd then 3z is odd, if z is even then 3z is even - sufficient

_________________

" Make more efforts "
Press Kudos if you liked my post

Intern
Joined: 10 Sep 2012
Posts: 2
Followers: 0

Kudos [?]: 5 [0], given: 0

### Show Tags

18 Oct 2012, 07:43
Went for A when I received it as question of the day since 2. 49 is odd seemed quite irrelevant to solve the question. But when I saw the actual question I knew it had to be D
Intern
Status: Life begins at the End of your Comfort Zone
Joined: 31 Jul 2011
Posts: 47
Location: Tajikistan
Concentration: General Management, Technology
GPA: 3.86
Followers: 1

Kudos [?]: 24 [0], given: 4

### Show Tags

18 Oct 2012, 11:42
Here we go:
z/3 is odd, hence z is odd, it could be 3 or any odd number multiplied by 3. - keep A
3*z - is odd, it could be look above, hence the answer is (D) each answer choices is sufficient. Did not delve deep since it is data sufficiency quesiton
Correct me, if I went awry.

vishy007 wrote:
Is integer $$Z$$ odd?

1. $$\frac{Z}{3}$$ is odd
2. $$3Z$$ is odd

[Reveal] Spoiler: OA
D

Source: GMAT Club Tests - hardest GMAT questions

Here OA is D with explanation S2 also implies that $$Z$$ is odd.

Why can't S2 be a fraction? For example 5/3.

I think answer to this question needs to be changed.

_________________

Intern
Joined: 01 Jun 2012
Posts: 26
Concentration: Entrepreneurship, Social Entrepreneurship
WE: Information Technology (Consulting)
Followers: 0

Kudos [?]: 5 [0], given: 4

### Show Tags

19 Oct 2012, 12:50
I concur. Both the options 1 & 2 are based on the rule odd * odd = odd. Kind of easy to crack.
Intern
Joined: 09 Jul 2013
Posts: 23
Location: United States (WA)
Schools: Foster '18 (M)
GMAT 1: 710 Q44 V44
GPA: 3.65
WE: Military Officer (Military & Defense)
Followers: 0

Kudos [?]: 16 [0], given: 15

### Show Tags

17 Oct 2013, 10:47
D.

Apply the following rules when evaluating this question.

Even integer x any integer (Even OR odd) = Even integer
(example: 2 x 2 = 4, 2 x 3 = 6)
Odd integer x Odd integer = Odd integer.
(example: 3 x 3 = 9)

On to the question:

Given: You can't rephrase the question, just note that Z is an integer - and we're answering a "Yes/No" question type.

Statement 1:
z/3 = some odd number. So z = 3xodd number (which is odd x odd). Sufficient. ("yes", z is odd)

Statement 2:
3z = some odd number. So, z must be odd. If z were even, then 3z would be even (refer to rule 1 above). Sufficient. ("yes", z is odd)

Both statements are sufficient, so D.
Manager
Joined: 18 Jan 2012
Posts: 51
Location: United States
Followers: 3

Kudos [?]: 81 [0], given: 26

### Show Tags

19 Oct 2013, 07:08
Here are a few equations that one needs to absolutely remember. One would be surprised at the number of questions in which these concepts can be applied.

[*]ODD x ODD = ODD
The only way to get an odd integer as a result when 2 integers are multiplied is when BOTH the integers are ODD.

As a consequence of the above rule, the division rule also applies
[*]ODD/ODD = ODD

ODD x EVEN = EVEN
ODD + ODD = EVEN
ODD - ODD = EVEN
ODD + EVEN = ODD
ODD - EVEN = ODD

_________________

-----------------------------------------------------------------------------------------------------
IT TAKES QUITE A BIT OF TIME AND TO POST DETAILED RESPONSES.
YOUR KUDOS IS VERY MUCH APPRECIATED

-----------------------------------------------------------------------------------------------------

Intern
Joined: 29 Sep 2013
Posts: 11
GMAT Date: 12-08-2014
Followers: 0

Kudos [?]: 3 [0], given: 13

### Show Tags

07 Nov 2013, 05:13
Z cannot be a fraction. when GMAT question says 3Z is odd. It is a true statement. For 3Z (or Z/3) to be odd, 3Z (or Z/3) should be an integer. For 3Z (or Z/3) to be an integer, Z should be an integer.
From my point of view answer to this question is B. For Z/3 to be odd Z should be a multiple of 3 (like 3,6, 9, 12....) if Z is 3,9,15... result will be odd. otherwise, it is even. So, this statement is not sufficient to answer if Z is odd or not. Correct me if I am wrong.
Math Expert
Joined: 02 Sep 2009
Posts: 32549
Followers: 5632

Kudos [?]: 68314 [0], given: 9797

### Show Tags

07 Nov 2013, 05:42
Expert's post
winwin02 wrote:
Z cannot be a fraction. when GMAT question says 3Z is odd. It is a true statement. For 3Z (or Z/3) to be odd, 3Z (or Z/3) should be an integer. For 3Z (or Z/3) to be an integer, Z should be an integer.
From my point of view answer to this question is B. For Z/3 to be odd Z should be a multiple of 3 (like 3,6, 9, 12....) if Z is 3,9,15... result will be odd. otherwise, it is even. So, this statement is not sufficient to answer if Z is odd or not. Correct me if I am wrong.

z cannot be a fraction because the stem says that z IS an integer: "is integer z odd?".

Next, if we were not told that z is an integer, then the answer would be A:

(1) $$\frac{z}{3}$$ is odd --> $$\frac{z}{3}=odd$$ --> $$z=3*odd=odd$$. Sufficient.

(2) $$3z$$ is odd --> $$3z=odd$$. Now, if z IS an integer, then it must be odd but if z is say 1/3 (in this case 3z=3*1/3=1=odd), then z is not an odd integer. Not sufficient.

Hope it's clear.
_________________
Intern
Joined: 29 Sep 2013
Posts: 11
GMAT Date: 12-08-2014
Followers: 0

Kudos [?]: 3 [0], given: 13

### Show Tags

07 Nov 2013, 06:53
Bunuel wrote:
winwin02 wrote:
Z cannot be a fraction. when GMAT question says 3Z is odd. It is a true statement. For 3Z (or Z/3) to be odd, 3Z (or Z/3) should be an integer. For 3Z (or Z/3) to be an integer, Z should be an integer.
From my point of view answer to this question is B. For Z/3 to be odd Z should be a multiple of 3 (like 3,6, 9, 12....) if Z is 3,9,15... result will be odd. otherwise, it is even. So, this statement is not sufficient to answer if Z is odd or not. Correct me if I am wrong.

z cannot be an integer because the stem says that z IS an integer: "is integer z odd?".

Next, if we were not told that z is an integer, then the answer would be B:

(1) $$\frac{z}{3}$$ is odd --> $$\frac{z}{3}=odd$$ --> $$z=3*odd=odd$$. Sufficient.

(2) $$3z$$ is odd --> $$3z=odd$$. Now, if z IS an integer, then it must be odd but if z is say 1/3 (in this case 3z=3*1/3=1=odd), then z is not an odd integer. Not sufficient.

Hope it's clear.

"Is integer Z odd?" means Z is integer (means not a fraction). Even/Odd applies to only integers.
What was is thinking about Z/3. When Z/3 is odd Z should be odd multiple of 3. So, Z is Odd. Sorry for that. Answer is D. Both (I) & (II) alone are sufficient
Re: m04 Q23   [#permalink] 07 Nov 2013, 06:53
Similar topics Replies Last post
Similar
Topics:
26 m04, Q 15 22 29 Oct 2008, 22:59
3 m04 #24 24 09 Oct 2008, 15:47
7 M04 #1 26 22 Sep 2008, 19:48
29 M04 # 32 15 22 Sep 2008, 19:43
23 M04 #12 93 10 Aug 2008, 12:56
Display posts from previous: Sort by

# m04 Q23

Moderator: Bunuel

 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®.