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

It is currently 17 Aug 2018, 06:04

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

If a is a positive even integer, and ab is a negative even integer, th

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

Hide Tags

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 47967
If a is a positive even integer, and ab is a negative even integer, th  [#permalink]

Show Tags

New post 05 Jul 2018, 21:45
1
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

18% (00:11) correct 82% (00:43) wrong based on 55 sessions

HideShow timer Statistics

If a is a positive even integer, and ab is a negative even integer, then b must be which of the following?

A. A negative number
B. A negative even integer
C. A negative integer
D. A positive even integer
E. A positive integer

_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Math Expert
User avatar
V
Joined: 02 Aug 2009
Posts: 6540
If a is a positive even integer, and ab is a negative even integer, th  [#permalink]

Show Tags

New post 05 Jul 2018, 23:08
Bunuel wrote:
If a is a positive even integer, and ab is a negative even integer, then b must be which of the following?

A. A negative number
B. A negative even integer
C. A negative integer
D. A positive even integer
E. A positive integer


let a = 4 ... take a as a multiple of 4 so that 'b' can be tested as a fraction
so 4b = -x where x is even integer..
if x = 2
\(4b=-x=-2..........b=\frac{-2}{4}=-\frac{1}{2}\) ..... b is a negative fraction
if x=4
\(4b=-x=-4..........b=\frac{-4}{4}=-1\) ..... b is a negative integer

A

even the choices give the answer away..
if a is positive and ab is negative.......b has to be negative
eliminate D and E

now negative numbers = ( negative fractions, negative integers, negative even integers, negative odd integers, )
so A consists of B and C as B and C are subset
so A itself would mean D and e

ans A
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html


GMAT online Tutor

Senior Manager
Senior Manager
User avatar
G
Status: Learning stage
Joined: 01 Oct 2017
Posts: 491
WE: Supply Chain Management (Energy and Utilities)
Premium Member CAT Tests
Re: If a is a positive even integer, and ab is a negative even integer, th  [#permalink]

Show Tags

New post 05 Jul 2018, 23:10
Bunuel wrote:
If a is a positive even integer, and ab is a negative even integer, then b must be which of the following?

A. A negative number
B. A negative even integer
C. A negative integer
D. A positive even integer
E. A positive integer


Given a=positive even
ab=negative even

For ab to be negative even , there are 3 cases of b:-
When a=18
1. b=-2, so ab=18*(-2)=-36 (here b is negative even integer)--------option D & E eliminated.
2. b=-3, so ab=18*(-3)=-54 (here b is negative odd integer)--------option B eliminated.
3. b=\(\frac{-1}{3}\), so ab=18*\(\frac{-1}{3}\)=-6 (here b is rational number)----------------option C eliminated.
Therefore, Since a*b is negative even & a is positive even, so 'b' is always a negative number.
Caution:- This is a MUST BE TRUE question.

Ans. (A)
_________________

Regards,

PKN

Rise above the storm, you will find the sunshine

Senior Manager
Senior Manager
User avatar
G
Joined: 14 Feb 2018
Posts: 380
Re: If a is a positive even integer, and ab is a negative even integer, th  [#permalink]

Show Tags

New post 06 Jul 2018, 03:24
1
PKN wrote:
Bunuel wrote:
If a is a positive even integer, and ab is a negative even integer, then b must be which of the following?

A. A negative number
B. A negative even integer
C. A negative integer
D. A positive even integer
E. A positive integer


Given a=positive even
ab=negative even

For ab to be negative even , there are 3 cases of b:-
When a=18
1. b=-2, so ab=18*(-2)=-36 (here b is negative even integer)--------option D & E eliminated.
2. b=-3, so ab=18*(-3)=-54 (here b is negative odd integer)--------option B eliminated.
3. b=\(\frac{-1}{3}\), so ab=18*\(\frac{-1}{3}\)=-6 (here b is rational number)----------------option C eliminated.
Therefore, Since a*b is negative even & a is positive even, so 'b' is always a negative number.
Caution:- This is a MUST BE TRUE question.

Ans. (A)


In my opinion the answer should be C. The question asks b "must be" what ? With your example 18*(-1/3) will result in an integer but 18*(-1/4) won't be an integer.

A would have been the answer if the question would have asked "could be". But the stem asks "must be". Thus, b must be a negative integer.

I would go with C.

Posted from my mobile device
Senior Manager
Senior Manager
User avatar
G
Status: Learning stage
Joined: 01 Oct 2017
Posts: 491
WE: Supply Chain Management (Energy and Utilities)
Premium Member CAT Tests
Re: If a is a positive even integer, and ab is a negative even integer, th  [#permalink]

Show Tags

New post 06 Jul 2018, 03:38
SonalSinha803 wrote:
PKN wrote:
Bunuel wrote:
If a is a positive even integer, and ab is a negative even integer, then b must be which of the following?

A. A negative number
B. A negative even integer
C. A negative integer
D. A positive even integer
E. A positive integer


Given a=positive even
ab=negative even

For ab to be negative even , there are 3 cases of b:-
When a=18
1. b=-2, so ab=18*(-2)=-36 (here b is negative even integer)--------option D & E eliminated.
2. b=-3, so ab=18*(-3)=-54 (here b is negative odd integer)--------option B eliminated.
3. b=\(\frac{-1}{3}\), so ab=18*\(\frac{-1}{3}\)=-6 (here b is rational number)----------------option C eliminated.
Therefore, Since a*b is negative even & a is positive even, so 'b' is always a negative number.
Caution:- This is a MUST BE TRUE question.

Ans. (A)


In my opinion the answer should be C. The question asks b "must be" what ? With your example 18*(-1/3) will result in an integer but 18*(-1/4) won't be an integer.

A would have been the answer if the question would have asked "could be". But the stem asks "must be". Thus, b must be a negative integer.

I would go with C.

Posted from my mobile device


Hi,

you have to choose 'b' judiciously so that ab will yield a negative even integer as per question.
So, in your case if \(b=\frac{-1}{4}\) and a=18(say), \(a*b=-\frac{18}{4}\) which violates the data provided in question.

So, choose (a,b) accordingly.

Hope it helps.
_________________

Regards,

PKN

Rise above the storm, you will find the sunshine

Re: If a is a positive even integer, and ab is a negative even integer, th &nbs [#permalink] 06 Jul 2018, 03:38
Display posts from previous: Sort by

If a is a positive even integer, and ab is a negative even integer, th

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

Events & Promotions

PREV
NEXT


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

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®.