It is currently 25 Jul 2017, 09:57

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Is the product of a and b odd?

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

Hide Tags

Expert Post
Math Expert
User avatar
D
Joined: 02 Sep 2009
Posts: 40376
Is the product of a and b odd? [#permalink]

Show Tags

New post 11 Nov 2014, 05:47
Expert's post
3
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

79% (01:39) correct 21% (00:43) wrong based on 122 sessions

HideShow timer Statistics

1 KUDOS received
Intern
Intern
User avatar
S
Joined: 24 Apr 2013
Posts: 16
Location: Russian Federation
GMAT ToolKit User
Re: Is the product of a and b odd? [#permalink]

Show Tags

New post 11 Nov 2014, 08:06
1
This post received
KUDOS
(1) a has only 2 factors => a is a prime number. It could be 2 (even) or 3 (odd). +No information about b.
Insufficient
(2) b = 2x + 1, where x is an integer => b=even+odd => b=odd. No information about a
Insufficient

Together: b is odd, and a can be either odd or even
(odd)(even)=even
(odd)(odd)=odd
Insufficient

Answer is E
1 KUDOS received
Manager
Manager
avatar
Joined: 10 Sep 2014
Posts: 99
Re: Is the product of a and b odd? [#permalink]

Show Tags

New post 11 Nov 2014, 10:59
1
This post received
KUDOS
Answer choice E!

Statement 1: not sufficient
A could be 2 (even) or other prime # (odd). We would need to know if B is even or odd to answer the question.

Statement 2: not sufficient
This tells us that B is odd since 2 times any number (even or odd) will be even. Add +1 to an even # and it will always be odd. We need to know if A is even or odd to answer the question.

Down to answer choices C and E.

When combined, we know that A is even or odd and that B is odd. If A is even, A*B would be even. If A is odd, A*B would be odd. Combined, the statements are not sufficient.

Answer choice E.
1 KUDOS received
Director
Director
User avatar
Joined: 25 Apr 2012
Posts: 728
Location: India
GPA: 3.21
WE: Business Development (Other)
Premium Member Reviews Badge
Re: Is the product of a and b odd? [#permalink]

Show Tags

New post 11 Nov 2014, 12:25
1
This post received
KUDOS
Bunuel wrote:

Tough and Tricky questions: Number Properties.



Is the product of a and b odd?

(1) a has only 2 factors
(2) b = 2x + 1, where x is an integer

Kudos for a correct solution.


The product will be odd if both a and b are odd
1. a has two factors so a is prime...now if a=2,b=odd number then product is not even but if a=any other prime and b=odd number than product is odd...clearly we dont have enough information.. Option A and D ruled out

b=2x+1 so possible values for b=1,3,5,7...b= odd number...B ruled out

Combining both statements we can still have product even or odd..

ans E
_________________


“If you can't fly then run, if you can't run then walk, if you can't walk then crawl, but whatever you do you have to keep moving forward.”

1 KUDOS received
Manager
Manager
avatar
Joined: 22 Sep 2012
Posts: 142
Concentration: Strategy, Technology
WE: Information Technology (Computer Software)
Re: Is the product of a and b odd? [#permalink]

Show Tags

New post 11 Nov 2014, 19:41
1
This post received
KUDOS
From 1, we can say a can be 2, 3, 5, 7 ... any prime number. Donot know the value of b. Therefore, insufficient

From 2, we can say b is odd. But we don't know a. Therefore, insufficient.

Combining a) and b), we can't say whether the product of a and b is odd or even, since it depends on the value of "a" which can either be even (value = 2) or odd (primes other than 2).

E) should be the answer
BSchool Forum Moderator
User avatar
P
Joined: 12 Aug 2015
Posts: 2184
GMAT ToolKit User Premium Member CAT Tests
Re: Is the product of a and b odd? [#permalink]

Show Tags

New post 14 Oct 2016, 06:10
Here we need to prove that A*B is odd
Note => It is not specified whether they are integers or not.
Statement 1 => A = prime => No clue of B
A=2 B=3 => A*B=even
A=3 B=5 => A*b= odd
Not suff
Statement 2 => B must be odd
no clue of A
not suff
combining them we can say if A is 2 then AB is even else Ab will be odd
since no boundary condition on A is given => not suff

Hence E
_________________

Give me a hell yeah ...!!!!!

Math Forum Moderator
User avatar
S
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 2960
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)
GMAT ToolKit User Premium Member
Is the product of a and b odd? [#permalink]

Show Tags

New post 15 Oct 2016, 08:05
Bunuel wrote:

Tough and Tricky questions: Number Properties.



Is the product of a and b odd?

(1) a has only 2 factors
(2) b = 2x + 1, where x is an integer

Kudos for a correct solution.


FROM STATEMENT - I INSUFFICIENT

a can be both Odd / Even ; further we have no knowledge of b so, we can not find ab

FROM STATEMENT - II INSUFFICIENT

If x = odd , 2x + 1 will be even
If x = even , 2x + 1 will be odd

Since a consistent value of b can not be determined we can not find the value of ab...

Thus, Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data specific to the problem are needed, answer will be (E)


_________________

Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )

Senior Manager
Senior Manager
avatar
B
Joined: 12 Nov 2016
Posts: 423
Re: Is the product of a and b odd? [#permalink]

Show Tags

New post 17 Jul 2017, 17:17
Bunuel wrote:

Tough and Tricky questions: Number Properties.



Is the product of a and b odd?

(1) a has only 2 factors
(2) b = 2x + 1, where x is an integer

Kudos for a correct solution.


This question is just asking- is "a" an even number - simple even and odd properties

Statement 1

This just means "a" is prime; but 2 is an even prime number

Statement 2
This just mean B must be odd because any number multiplied by an even number is even and the sum of an even and odd number is odd. But even if this statement forces B to be odd, we still cannot say what A is.

E
Re: Is the product of a and b odd?   [#permalink] 17 Jul 2017, 17:17
    Similar topics Author Replies Last post
Similar
Topics:
Experts publish their posts in the topic If a and b are positive integers, is the product ab odd? Bunuel 5 19 Apr 2017, 04:21
2 Experts publish their posts in the topic If a and b are integers, is ab an odd? MathRevolution 4 16 Jul 2017, 11:26
Experts publish their posts in the topic If a and b are integers, is a an odd number? MathRevolution 3 21 Oct 2016, 08:25
50 Experts publish their posts in the topic Is the product of two integers A and B odd? EgmatQuantExpert 31 12 May 2017, 06:24
2 Experts publish their posts in the topic Is the product of integers m and n odd? avohden 4 14 Oct 2013, 09:17
Display posts from previous: Sort by

Is the product of a and b odd?

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


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

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®.