BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

is xyz odd ?

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Data Sufficiency |
User avatar
Legendary Member
Posts: 1560
Joined: Tue Nov 17, 2009 2:38 amFollowed by: 5 members
Thanked: 137 times

by thephoenix » Thu Apr 08, 2010 6:29 am
IMO A
if any prime no. -z=odd no. then z is an even no.
becoz all prime no's except 2 are odd hence in order to get an odd z must be an even
hence xyz is not an odd no.
suff

s2) does not tells anything abt z
hence insuff
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 208
Joined: Sun Sep 28, 2008 12:30 pm
Thanked: 22 times

by neoreaves » Thu Apr 08, 2010 6:57 am
thephoenix wrote:IMO A
if any prime no. -z=odd no. then z is an even no.
becoz all prime no's except 2 are odd hence in order to get an odd z must be an even
hence xyz is not an odd no.
suff

s2) does not tells anything abt z
hence insuff
Nope....OA is C
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 1560
Joined: Tue Nov 17, 2009 2:38 amFollowed by: 5 members
Thanked: 137 times

by thephoenix » Thu Apr 08, 2010 7:07 am
is it x*y*z or xyz
do u have OE
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 12
Joined: Fri Mar 26, 2010 11:57 am

by [email protected] » Thu Apr 08, 2010 7:18 am
statement (1) says
Any prime number - Z = Positive Odd number
Z= Any prime number - Positive Odd number
=(5,7,11,13,17....) - (3,5,7,9....)
=is even
statement 1 is sufficient


statement (2)
if we take any number =X, then X+1=Prime, means X can be 1,4,6,10,12....... where X+1 is 2,5,7,11,13.....
since the original question already says X>Y>Z and all are positive integers, X is definitely greater than 1, which means X=4,6,10

It is given that XYZ is not divisible by 4, X can be 6,10....

SO statement 2 is sufficient


so answer should be D
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 610
Joined: Fri Jan 15, 2010 12:33 amFollowed by: 2 members
Thanked: 47 times

by kstv » Thu Apr 08, 2010 8:42 am
thephoenix wrote:is it x*y*z or xyz
do u have OE
either way if z is even xyz or x*y*z will be even.

if it is x*y*z then alteast two of them are odd otherwise it will be divisible by 4
(1) Any prime number - Z = Positive Odd number and z < y < x
so possible z = 1 (cos 2 is a prime no) or even nos. Insuff
(2) X +1 = Prime and X, Y, Z are positive integers X>Y>Z
x > 3 cos even if z = 1 x will be 3 but since x + 1 = prime no and all prime no except 2 is an odd no
x has to be an even number > 3 i.e. 4, 6, 8
so x*y*z will be an even no. Sufficient.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 126
Joined: Wed Jun 24, 2009 1:12 pm
Location: Montreal
Thanked: 2 times
GMAT Score:510

by ssuarezo » Thu Apr 08, 2010 8:50 am
Neoreaves,
what explanation did they give you to conclude it;s C?
Thanks
Silvia
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 1560
Joined: Tue Nov 17, 2009 2:38 amFollowed by: 5 members
Thanked: 137 times

by thephoenix » Thu Apr 08, 2010 9:37 am
kstv wrote: (2) X +1 = Prime and X, Y, Z are positive integers X>Y>Z
x > 3 cos even if z = 1 x will be 3 but since x + 1 = prime no and all prime no except 2 is an odd no
x has to be an even number > 3 i.e. 4, 6, 8
so x*y*z will be an even no. Sufficient.
Ok agreed with you soln for s1) but if its xyz a three digit no. then does s2) is sufficient , i dont think so
however the poster says OA is C
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 50
Joined: Tue Oct 13, 2009 1:25 am
Thanked: 14 times
GMAT Score:720

by November Rain » Thu Apr 08, 2010 10:24 am
1) Any prime number - Z = Positive Odd number
I think Statement 1 is wrong because otherwise its an impossible condition.

If the prime number is 2, then Z needs to be 1(odd) so that the result is a positive odd number

If the prime number is other than 2, then Z needs to be an even number so that the result is a positive odd number.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Newbie | Next Rank: 10 Posts
Posts: 1
Joined: Mon Mar 29, 2010 5:37 pm

by ISBcalling » Thu Apr 08, 2010 10:26 am
As XYZ is not divisible by 4 thus any of X,Y,Z can't be 4 or its multiple. On top of this, if any one is even, the other two has to be odd.

From option 1, Z = Any Prime no. - positive odd int ------------ Here prime no. can't be same as odd int but odd int cud be a prime.
=> Z = {(2-1), (3-1), (5-3), (7-1), (11-1), (11-5), (13-3), (13-7) etc} = {1, 2, 6, 10 etc}

Option 1 is insufficient as it shows z can be odd as well as even.

From Option 2, X+1 is prime. Here X can neither be 1 nor be 2 as X>Y>Z and all are positive integers.
X can be 3, 6, 10, 18 etc but can't be 4 or its multiple.

Option 2 is also insufficient as X can be odd as well as even.

Combining Option 1 & 2, X+1 is prime & Z = Any prime no. - positive int.

Both X & Z can't be even. If X = 3, Z could only be 1.
If X = 6, Z could be only 1 & can't be 2.
If X = 10, Z could be only 1.

X could be both odd as well as even, Z will be only 1.

Thus Option 1 & 2 together is also insufficient.

My Answer is E.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 3225
Joined: Tue Jan 08, 2008 2:40 pmFollowed by: 614 members
Location: Toronto
Thanked: 1710 times
GMAT Score:800

by Stuart@KaplanGMAT » Thu Apr 08, 2010 10:45 am
neoreaves wrote:Is XYZ an odd number? Where X, Y, Z are positive integers
Such that XYZ is not divisible by 4 and X>Y>Z

1) Any prime number - Z = Positive Odd number
2) X +1 = Prime
The question isn't formatted as a GMAT question would be - on the GMAT, the extra information in the stem always precedes the question. For example:
If X, Y and Z are positive integers, XYZ is not divisible by 4 and X > Y > Z, is XYZ odd?
What's the source? Statement (1) provides an impossible condition, so you (and others) should be very wary of this source in the future.

Always citing your sources accomplishes 3 things:

1) you give credit to the question creator, thereby avoiding plagiarism issues;
2) you tell the reader how credible (i.e. "GMATesque") the question is; and
3) you help people avoid unreliable sources in the future.
Image

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 3225
Joined: Tue Jan 08, 2008 2:40 pmFollowed by: 614 members
Location: Toronto
Thanked: 1710 times
GMAT Score:800

by Stuart@KaplanGMAT » Thu Apr 08, 2010 10:49 am
ISBcalling wrote: From Option 2, X+1 is prime. Here X can neither be 1 nor be 2 as X>Y>Z and all are positive integers.
X can be 3, 6, 10, 18 etc but can't be 4 or its multiple.

Option 2 is also insufficient as X can be odd as well as even.
One small math point (even though this is a bad question, we can still learn a few things from it!):

if X+1 is prime, then x could be:

1, 2, 4, 6, 10, ...

However, since X>Y>Z>0, the smallest possible value of X (ignoring statement (2)) is 3.

So, the values of X based on statement (2) are:

4, 6, 10, 12, ....

every one of which is even.

(We could also eliminate all the multiples of 4, but that's irrelevant to answering the question.)

If X must be even, then XYZ will always be even as well, providing a definite "no" answer to the original question.

Accordingly, (2) is sufficient alone.

(Statement (1) is impossible, since there's no value of Z that fits the condition given, so there's no sense evaluation (1).)
Image

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 208
Joined: Sun Sep 28, 2008 12:30 pm
Thanked: 22 times

by neoreaves » Fri Apr 09, 2010 1:26 am
again the source is some other forum ...... but then again isnt the purpose of a forum to discuss ...no matter how absurd a question is ...the important thing is to find the right answer ....... it was not my intention to lead people astray in case it was a non GMAT-esque question ........but again if i have encountered a problem quoted on some forum by someone and it confused me ....why not discuss it out with everyone ....it clears my concepts as well as other people's concepts .....i am sure discussing a bad question is still better than not discussing it ....

Moreoever, i know such questions with the incorrect OA can confuse us but with valuable feedbacks specially from Instructors we can see our way through ...which was the same in this case .....


I agree the question is not very GMAT-esque ...and if it was then OA should be B ..though statement 1 is impossible
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 610
Joined: Fri Jan 15, 2010 12:33 amFollowed by: 2 members
Thanked: 47 times

by kstv » Fri Apr 09, 2010 2:17 am
I may have just scratched the surface of GMAT , forget Beating it . Still, I do feel stating the source is imp. Even if you state at the beginning that you are not sure of the source.
Then one does not get psyched if you do not make progress after spending 5 mins on one Q.

Try solving a dubious SC Q in verbal, you may just end up with a wrong concept.
There are some grammer rules which are unique to GMAT or so I console myself.

Yes, nothing like thrashing out wrong concepts at this forum.
Hope to see more posts from you.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 21
Joined: Wed Jun 11, 2008 8:18 pm
Thanked: 3 times

by vcb » Fri Apr 09, 2010 7:12 am
I think I am missing something, but cant put a finger on it. Stmt 1 says:

1) Any prime number - Z = Positive Odd number

Not able to figure out why it is impossible - what if Z = 2? any other Prime number would be an odd number.

This implies the difference would be a Positive odd number, since Z is the least of the three.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply