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

 It is currently 22 Aug 2018, 00:57

### 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

# If positive integers a and b are both odd, which of the following must

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 48119
If positive integers a and b are both odd, which of the following must  [#permalink]

### Show Tags

10 Dec 2016, 06:25
00:00

Difficulty:

25% (medium)

Question Stats:

68% (00:43) correct 32% (00:39) wrong based on 229 sessions

### HideShow timer Statistics

If positive integers a and b are both odd, which of the following must not be odd?

A. ab
B. a(ab)
C. b – a – 1
D. (a + b)/2
E. a – b

_________________
Current Student
Joined: 12 Aug 2015
Posts: 2650
Schools: Boston U '20 (M)
GRE 1: Q169 V154
Re: If positive integers a and b are both odd, which of the following must  [#permalink]

### Show Tags

10 Dec 2016, 06:29
Manager
Joined: 02 Nov 2013
Posts: 91
Location: India
Re: If positive integers a and b are both odd, which of the following must  [#permalink]

### Show Tags

10 Dec 2016, 09:10
1
If positive integers a and b are both odd.
A. ab ----- Odd * Odd = Odd
B. a(ab)-- Odd * Odd * Odd = Odd
C. b – a – 1 -- Odd - Odd - 1 = Odd
D. (a + b)/2 -- Odd + Odd / 2 = Odd
E. a – b ---- Odd - Odd = Even in all the cases. Hence answer is E.
Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 3819
Location: India
GPA: 3.5
Re: If positive integers a and b are both odd, which of the following must  [#permalink]

### Show Tags

10 Dec 2016, 09:41
1
Bunuel wrote:
If positive integers a and b are both odd, which of the following must not be odd?

A. ab
B. a(ab)
C. b – a – 1
D. (a + b)/2
E. a – b

A. ODD * ODD = ODD

B. ODD(ODD*ODD) = ODD

C. ODD - ODD = EVEN - 1 = ODD

D. ODD + ODD = EVEN/2 = EVEN/ODD

E. ODD - ODD = EVEN

So, Correct 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 )

Manager
Joined: 18 Oct 2016
Posts: 139
Location: India
WE: Engineering (Energy and Utilities)
Re: If positive integers a and b are both odd, which of the following must  [#permalink]

### Show Tags

17 Apr 2017, 02:40
Option E

a & b are Odd integers. Odd: O, Even: E & Fraction: F.

A. ab = O*O = O
B. a(ab) = O(O*O) = O
C. b – a – 1 = O - O - 1 = E - 1 = O
D. (a + b)/2 = (O + O)/2 = E/2 = O
E. a – b = O - O = E
_________________

Press Kudos if you liked the post!

Status: The final countdown
Joined: 17 Feb 2014
Posts: 48
Concentration: Strategy, General Management
GMAT 2: 660 Q37 V33
GPA: 3.13
WE: Operations (Commercial Banking)
Re: If positive integers a and b are both odd, which of the following must  [#permalink]

### Show Tags

23 Apr 2017, 00:18
A. o1*o2=o
B. o1(o1*o2)=o
C. o2-o1-1=o
D. (o1+o2)/2=o
E. o1-o2=e

Hence E
Intern
Joined: 30 Jul 2016
Posts: 6
Re: If positive integers a and b are both odd, which of the following must  [#permalink]

### Show Tags

20 Jun 2017, 07:51
How come D is not the answer if we apply 3+5/2=4 , therefore even?

Bunuel wrote:
If positive integers a and b are both odd, which of the following must not be odd?

A. ab
B. a(ab)
C. b – a – 1
D. (a + b)/2
E. a – b
Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 3819
Location: India
GPA: 3.5
Re: If positive integers a and b are both odd, which of the following must  [#permalink]

### Show Tags

20 Jun 2017, 08:02
Yoohanna wrote:
How come D is not the answer if we apply 3+5/2=4 , therefore even?

Bunuel wrote:
If positive integers a and b are both odd, which of the following must not be odd?

A. ab
B. a(ab)
C. b – a – 1
D. (a + b)/2
E. a – b

Good observation, thats why I mentioned the result of (D) may/may not be EVEN
Abhishek009 wrote:
D. ODD + ODD = EVEN/2 = EVEN/ODD

You have considered the numbers as 3 and 5 , see if I take the numbers as 1 and 5

$$\frac{(a + b)}{2} = \frac{6}{2} = 3 (ODD)$$

Thus, (D) may/may not be even...

_________________

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 )

EMPOWERgmat Instructor
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 12226
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: If positive integers a and b are both odd, which of the following must  [#permalink]

### Show Tags

04 Dec 2017, 14:24
Hi All,

This question can be approached with Number Property rules. We're told that A and B are both ODD, POSITIVE INTEGERS. We're asked which of the following MUST NOT be odd.

Answer A: (A)(B) = (odd)(odd) = odd
Answer B: (A)(A)(B) = (odd)(odd)(odd) = odd
Answer C: B - A - 1 = (odd) - (odd) - (odd) = odd
Answer D: (A+ B)/2 = (odd + odd)/2 = (even)/2 = COULD be even (re: 4/2 = 2) OR odd (re: 6/2 = 3)
Answer E: A - B = (odd) - (odd) = EVEN

There's only one answer that can NEVER be odd.

GMAT assassins aren't born, they're made,
Rich
_________________

760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

# Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save \$75 + GMAT Club Tests Free
Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 3199
Location: United States (CA)
Re: If positive integers a and b are both odd, which of the following must  [#permalink]

### Show Tags

11 Jan 2018, 14:45
Bunuel wrote:
If positive integers a and b are both odd, which of the following must not be odd?

A. ab
B. a(ab)
C. b – a – 1
D. (a + b)/2
E. a – b

Since odd - odd = even, answer choice E, a - b is not odd.

_________________

Scott Woodbury-Stewart
Founder and CEO

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Re: If positive integers a and b are both odd, which of the following must &nbs [#permalink] 11 Jan 2018, 14:45
Display posts from previous: Sort by

# Events & Promotions

 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®.