It is currently 23 Oct 2017, 10:54

### 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

# If x and y are integers, is the value of x(y + 1) even?

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

### Hide Tags

Director
Joined: 29 Nov 2012
Posts: 868

Kudos [?]: 1416 [1], given: 543

If x and y are integers, is the value of x(y + 1) even? [#permalink]

### Show Tags

16 Mar 2013, 03:52
1
KUDOS
8
This post was
BOOKMARKED
00:00

Difficulty:

65% (hard)

Question Stats:

48% (00:44) correct 52% (00:41) wrong based on 426 sessions

### HideShow timer Statistics

If x and y are integers, is the value of x(y + 1) even?

(1) x and y are prime numbers.
(2) y > 7

[Reveal] Spoiler:
Why is the answer C I'm getting E aren't there multiple cases when the statements are combined?
[Reveal] Spoiler: OA

_________________

Click +1 Kudos if my post helped...

Amazing Free video explanation for all Quant questions from OG 13 and much more http://www.gmatquantum.com/og13th/

GMAT Prep software What if scenarios http://gmatclub.com/forum/gmat-prep-software-analysis-and-what-if-scenarios-146146.html

Last edited by Bunuel on 16 Mar 2013, 03:56, edited 1 time in total.
Edited the question.

Kudos [?]: 1416 [1], given: 543

Math Expert
Joined: 02 Sep 2009
Posts: 41913

Kudos [?]: 129476 [0], given: 12201

Re: If x and y are integers, is the value of x(y + 1) even? [#permalink]

### Show Tags

16 Mar 2013, 04:02
Expert's post
2
This post was
BOOKMARKED
fozzzy wrote:
If x and y are integers, is the value of x(y + 1) even?

(1) x and y are prime numbers.
(2) y > 7

Why is the answer C I'm getting E aren't there multiple cases when the statements are combined?

Please hide OA under the spoiler.

If x and y are integers, is the value of x(y + 1) even?

x(y + 1) will be even if x is even or/and y is odd.

(1) x and y are prime numbers. If x is ANY odd prime and y is an even prime, so 2, then x(y + 1) = odd*(even+1) = odd*odd=odd but in all other cases x(y + 1) = even. Not sufficient.

(2) y > 7. Clearly insufficient.

(1)+(2) Since y = prime > 7, then y = odd, thus x(y + 1) = x(odd + 1) = x*even = even. Sufficient.

Hope it's clear.
_________________

Kudos [?]: 129476 [0], given: 12201

Director
Joined: 29 Nov 2012
Posts: 868

Kudos [?]: 1416 [0], given: 543

Re: If x and y are integers, is the value of x(y + 1) even? [#permalink]

### Show Tags

16 Mar 2013, 06:27
Thanks missed the prime part silly error. I don't know how to insert the second spoiler... I'll do that next time around.
_________________

Click +1 Kudos if my post helped...

Amazing Free video explanation for all Quant questions from OG 13 and much more http://www.gmatquantum.com/og13th/

GMAT Prep software What if scenarios http://gmatclub.com/forum/gmat-prep-software-analysis-and-what-if-scenarios-146146.html

Kudos [?]: 1416 [0], given: 543

VP
Status: Final Lap Up!!!
Affiliations: NYK Line
Joined: 21 Sep 2012
Posts: 1077

Kudos [?]: 649 [0], given: 70

Location: India
GMAT 1: 410 Q35 V11
GMAT 2: 530 Q44 V20
GMAT 3: 630 Q45 V31
GPA: 3.84
WE: Engineering (Transportation)
Re: If x and y are integers, is the value of x(y + 1) even? [#permalink]

### Show Tags

16 Mar 2013, 06:36
fozzzy wrote:
Thanks missed the prime part silly error. I don't know how to insert the second spoiler... I'll do that next time around.

Hey
One quick point here all primes except 2, when 1 is added will give an even number.
Statement provides a clue for the above, So when it is greater than 7 the constraint of 2 is avoided.....and hence the answer is C

Consider Kudos if my post helps.

Archit

Kudos [?]: 649 [0], given: 70

GMAT Club Legend
Joined: 09 Sep 2013
Posts: 16534

Kudos [?]: 274 [0], given: 0

Re: If x and y are integers, is the value of x(y + 1) even? [#permalink]

### Show Tags

21 Oct 2014, 09:27
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

Kudos [?]: 274 [0], given: 0

GMAT Club Legend
Joined: 09 Sep 2013
Posts: 16534

Kudos [?]: 274 [0], given: 0

Re: If x and y are integers, is the value of x(y + 1) even? [#permalink]

### Show Tags

20 Sep 2016, 23:54
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

Kudos [?]: 274 [0], given: 0

SVP
Joined: 12 Sep 2015
Posts: 1798

Kudos [?]: 2476 [2], given: 357

Re: If x and y are integers, is the value of x(y + 1) even? [#permalink]

### Show Tags

28 Sep 2016, 16:27
2
KUDOS
Expert's post
Top Contributor
fozzzy wrote:
If x and y are integers, is the value of x(y + 1) even?

(1) x and y are prime numbers.
(2) y > 7

Having scanned the two statements, I can see that this question is ultimately testing whether or not we recognize that ALL prime numbers are odd EXCEPT for 2 (which is even).

Target question: Is x(y+1) an even number?

Statement 1: x and y are prime numbers.
There are several values of x and y that satisfy this condition. Here are two:
Case a: x = 2 and y = 3, in which case x(y+1) is EVEN
Case b: x = 3 and y = 2, in which case x(y+1) is ODD
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: y > 7
There are several values of x and y that satisfy this condition. Here are two:
Case a: x = 2 and y = 8, in which case x(y+1) is EVEN
Case b: x = 3 and y = 8, in which case x(y+1) is ODD
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
If y is a prime number and y > 7, we know that y MUST BE ODD
If y is odd, then y+1 must be EVEN
This means that x(y+1) = x(some EVEN integer) = EVEN
So, x(y+1) is definitely even
Since we can answer the target question with certainty, the combined statements are SUFFICIENT

[Reveal] Spoiler:
C

RELATED VIDEOS

_________________

Brent Hanneson – Founder of gmatprepnow.com

Kudos [?]: 2476 [2], given: 357

Intern
Joined: 24 Nov 2015
Posts: 18

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

Re: If x and y are integers, is the value of x(y + 1) even? [#permalink]

### Show Tags

13 Jul 2017, 00:41
In my opinion, this type of problem is super easy if you really understand what you're being asked, and then re-frame the question to be more straightforward.

Original Question: Is x(y+1) even?

For x(y+1) to be even, either "x", or "y+1" must be even. So we're really asking, "Is either "x" or "y+1" even?

Well, we can simplify that even further. If "y+1" is even, then "y" is odd. So the new question becomes:

"Do we know whether either "x" is even, or "y" is odd?

A.) x and y are prime numbers.

Remember that "2" is a prime number, so "x" could be the even number 2, or it could be the odd number 3,or 5, or 7, etc. Same goes for "y".

This is not enough information to answer the question: "Do we know whether either "x" is even, or "y" is odd?

INSUFFICIENT.

B.) y > 7

This tells us nothing about "x," and it does not tell us whether "y" is even or odd. (There are many even and odd numbers greater than 7. For example, 8 is even, and 9 is odd.)

This is not enough information to answer the question: "Do we know whether either "x" is even, or "y" is odd?

INSUFFICIENT.

C.) If we know that "x" and "y" are prime, AND we know that "y" is greater than 7, then we know that "y" is NOT 2, and therefore "y" is odd. (every prime number above 2 is odd). Since we know that "y" is odd...

This is enough to answer the question "Do we know whether either "x" is even, or "y" is odd?

SUFFICIENT.

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

Re: If x and y are integers, is the value of x(y + 1) even?   [#permalink] 13 Jul 2017, 00:41
Display posts from previous: Sort by

# If x and y are integers, is the value of x(y + 1) even?

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

 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®.