Summer is Coming! Join the Game of Timers Competition to Win Epic Prizes. Registration is Open. Game starts Mon July 1st.

 It is currently 22 Jul 2019, 01:35 ### 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

#### Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.  # If positive integers a and b are both odd, which of the following must

Author Message
TAGS:

### Hide Tags

Math Expert V
Joined: 02 Sep 2009
Posts: 56342
If positive integers a and b are both odd, which of the following must  [#permalink]

### Show Tags 00:00

Difficulty:   25% (medium)

Question Stats: 69% (00:59) correct 31% (00:54) wrong based on 254 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 D
Joined: 12 Aug 2015
Posts: 2609
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

Odd -Odd => Even
Hence E can never be even.

Hence E

_________________
Manager  B
Joined: 02 Nov 2013
Posts: 81
Location: India
Re: If positive integers a and b are both odd, which of the following must  [#permalink]

### Show Tags

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 P
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4512
Location: India
GPA: 3.5
Re: If positive integers a and b are both odd, which of the following must  [#permalink]

### Show Tags

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  S
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

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! B
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

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

### Show Tags

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 P
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4512
Location: India
GPA: 3.5
Re: If positive integers a and b are both odd, which of the following must  [#permalink]

### Show Tags

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 V
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 14609
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

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

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

# Rich Cohen

Co-Founder & GMAT Assassin Follow
Special Offer: Save \$75 + GMAT Club Tests Free
Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/
Target Test Prep Representative D
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 6967
Location: United States (CA)
Re: If positive integers a and b are both odd, which of the following must  [#permalink]

### Show Tags

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

Scott@TargetTestPrep.com

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

If you find one of my posts helpful, please take a moment to click on the "Kudos" button. Re: If positive integers a and b are both odd, which of the following must   [#permalink] 11 Jan 2018, 14:45
Display posts from previous: Sort by

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