It is currently 22 Feb 2018, 16:55

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

If a,b, and c are prime numbers, do (a+b) and c have a common factor

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

Hide Tags

1 KUDOS received
Intern
Intern
avatar
Joined: 15 Dec 2015
Posts: 5
Concentration: Sustainability, Strategy
GMAT ToolKit User
If a,b, and c are prime numbers, do (a+b) and c have a common factor [#permalink]

Show Tags

New post 26 Apr 2016, 17:01
1
This post received
KUDOS
14
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

67% (00:45) correct 33% (00:38) wrong based on 441 sessions

HideShow timer Statistics

If a,b, and c are prime numbers, do \((a+b)\) and \(c\) have a common factor that is greater than 1?

(1) a,b, and c are all different prime numbers
(2) \(c\neq{2}\)
[Reveal] Spoiler: OA
Expert Post
7 KUDOS received
Math Expert
User avatar
D
Joined: 02 Aug 2009
Posts: 5660
If a,b, and c are prime numbers, do (a+b) and c have a common factor [#permalink]

Show Tags

New post 26 Apr 2016, 19:08
7
This post received
KUDOS
Expert's post
4
This post was
BOOKMARKED
amitpaul527 wrote:
If a,b, and c are prime numbers, do \((a+b)\) and \(c\) have a common factor that is greater than 1?

(1) a,b, and c are all different prime numbers
(2) \(c\neq{2}\)


Hi,

lets analyze the Q


1) If all three are same prime ans will be YES.. -- (3+3)=6 and 3-- factors 1 and 3

2) If all are different, and c is 2.. ans is YES -- (3+7) = 10, always be EVEN and 2--- 2 will be factor

3) If all are different and a or b is 2, ans can be both YES or NO..
(2+3) = 5 and c=5..YES
(2+7) =9 and c=11..NO

4) If all are different and none of them is 2.. ans will be again YES or NO..
(3+5)=8... c=7..NO
(3+7) = 10.. c=5.. YES

lets see the statements
(1) a,b, and c are all different prime numbers
Any of the above 3 conditions can exist -(2),(3)and (4)
Insuff

(2) \(c\neq{2}\)
any of the above cases (1), (3) and (4) can exist..
Insuff

Combined-
3 and 4 cases still exist
Insuff
E
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html


BANGALORE/-

Intern
Intern
avatar
Joined: 31 Mar 2016
Posts: 5
If a, b, and c are prime numbers, do (a+b) and c have a common factor [#permalink]

Show Tags

New post 04 Jun 2016, 07:00
1
This post was
BOOKMARKED
If a, b, and c are prime numbers, do (a+b) and c have a common factor that is greater than 1?

(1) a, b, and c are all different prime numbers
(2) c does not equal to 2
Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43867
Re: If a,b, and c are prime numbers, do (a+b) and c have a common factor [#permalink]

Show Tags

New post 04 Jun 2016, 10:52
Intern
Intern
User avatar
Joined: 11 Apr 2015
Posts: 36
Location: Germany
Concentration: General Management, Entrepreneurship
GPA: 3.1
WE: Project Management (Energy and Utilities)
Re: If a,b, and c are prime numbers, do (a+b) and c have a common factor [#permalink]

Show Tags

New post 27 Jun 2016, 03:55
chetan2u wrote:
amitpaul527 wrote:
If a,b, and c are prime numbers, do \((a+b)\) and \(c\) have a common factor that is greater than 1?

(1) a,b, and c are all different prime numbers
(2) \(c\neq{2}\)


Hi,

lets analyze the Q


1) If all three are same prime ans will be NO.. -- (3+3)=6 and 3-- factors 1 and 3




chetan2u, can you please explain why the answer is no when the primes are all the same. 3 is the common factor of 3 and 6, so the answer should be yes. What am I missing? Sorry if the question is confusing, my brain is fried right now.
_________________

"I fear not the man who has practiced 10,000 kicks once, but I fear the man who has practiced one kick 10,000 times." Bruce Lee

"I hated every minute of training, but I said, "Don’t quit. Suffer now and live the rest of your life as a champion."" Muhammad Ali

Intern
Intern
avatar
B
Joined: 18 Jan 2012
Posts: 40
Re: If a,b, and c are prime numbers, do (a+b) and c have a common factor [#permalink]

Show Tags

New post 17 Jul 2016, 08:14
Each statement alone is not sufficient. Combined, two possibilities:
If (a+b) = (2+3) and c is 5 (c must be different from 2) they will have a common factor of 5
If (a+b) = 11+7 and c is 5, they will NOT have a common factor.

For Yes/No DS questions, we need to have a definitive Yes or a definitive No. Combined - not sufficient. Answer E.
Current Student
User avatar
Joined: 18 Oct 2014
Posts: 902
Location: United States
GMAT 1: 660 Q49 V31
GPA: 3.98
GMAT ToolKit User
Re: If a,b, and c are prime numbers, do (a+b) and c have a common factor [#permalink]

Show Tags

New post 17 Jul 2016, 10:06
amitpaul527 wrote:
If a,b, and c are prime numbers, do \((a+b)\) and \(c\) have a common factor that is greater than 1?

(1) a,b, and c are all different prime numbers
(2) \(c\neq{2}\)


(1) a,b, and c are all different prime numbers
if a=3, b=2 and c=5, then no

if a = 3, b= 5 and c=7, then yes.

Not sufficient

(2) \(c\neq{2}\)[/quote]
if a=3, b=2 and c=5, then no

if a = 3, b= 5 and c=7, then yes.

Not sufficient.

Combining both statements is also not sufficient.

E is the answer
_________________

I welcome critical analysis of my post!! That will help me reach 700+

Retired Moderator
User avatar
P
Joined: 12 Aug 2015
Posts: 2424
GRE 1: 323 Q169 V154
GMAT ToolKit User Premium Member
Re: If a,b, and c are prime numbers, do (a+b) and c have a common factor [#permalink]

Show Tags

New post 21 Aug 2016, 09:25
taking a=2 b=3 and c=7 we can discard both the statements as well as there combination
SMASH that E
_________________


Getting into HOLLYWOOD with an MBA

Stone Cold's Mock Tests for GMAT-Quant(700+)

Intern
Intern
avatar
B
Joined: 19 May 2016
Posts: 29
Location: United States
Concentration: Strategy, Human Resources
GMAT 1: 710 Q46 V41
GMAT 2: 730 Q49 V41
GMAT 3: 680 Q46 V37
WE: Operations (Manufacturing)
Reviews Badge
Re: If a,b, and c are prime numbers, do (a+b) and c have a common factor [#permalink]

Show Tags

New post 14 May 2017, 15:55
Hi Banuel,

I got this question right, but I was wondering if statement 2 said that neither a, b, or c could be 2, that would be sufficient, right?

Thank you!
Intern
Intern
avatar
Joined: 13 May 2017
Posts: 8
Re: If a,b, and c are prime numbers, do (a+b) and c have a common factor [#permalink]

Show Tags

New post 14 May 2017, 16:05
Example 17 , 19, 3
17+19= 36 which is divisible by 3
But 19+3 = 22 , not divisible by 17
Therefore statement 2 is not sufficient
Correct answer is E

Sent from my Coolpad 3600I using GMAT Club Forum mobile app
2 KUDOS received
Retired Moderator
User avatar
P
Joined: 12 Aug 2015
Posts: 2424
GRE 1: 323 Q169 V154
GMAT ToolKit User Premium Member
Re: If a,b, and c are prime numbers, do (a+b) and c have a common factor [#permalink]

Show Tags

New post 14 May 2017, 16:07
2
This post received
KUDOS
toby001 wrote:
Hi Banuel,

I got this question right, but I was wondering if statement 2 said that neither a, b, or c could be 2, that would be sufficient, right?

Thank you!



Nopes.
The answer would still be E.


Let us modify the question =-->

If a,b, and c are prime numbers, do (a+b) and c have a common factor that is greater than 1?
(1) a,b, and c are all different prime numbers
(2) c≠2


Statment 1 --> 2,3,5 => YES
3,5,13 => NO

Hence not sufficient,

Statment 2 --> What if the primes are equal ?
We need to consider the possibility when a=b=c
Say z=b=c=7
So a+b=14
c=7
Clearly GCD≠1
Hence not sufficient.

Now combing the two statements => as a,c,b≠2
They are all odd primes.
Still -> 3,5,7 => YES
3,5,11 => NO

Hence not sufficient.

_________________


Getting into HOLLYWOOD with an MBA

Stone Cold's Mock Tests for GMAT-Quant(700+)

Senior SC Moderator
User avatar
D
Joined: 14 Nov 2016
Posts: 1277
Location: Malaysia
GMAT ToolKit User Premium Member CAT Tests
If a,b, and c are prime numbers, do (a+b) and c have a common factor [#permalink]

Show Tags

New post 14 May 2017, 18:03
amitpaul527 wrote:

TRICKY


If a,b, and c are prime numbers, do \((a+b)\) and \(c\) have a common factor that is greater than 1?

(1) a,b, and c are all different prime numbers
(2) \(c\neq{2}\)


If you only know that they're all prime

You could have c = 2, a + b = 3 + 5 = 8

So they'd have a common factor

When S2 says c ≠ 2, that's a clue to try c = 2 in S1.

You could also try c = 3, a = 2, b = 7

Since c is prime, the question is whether c is a factor of ( a+b ), so you want to try to find ways to make c a factor of a+b.

If a = 2, b = 7, c = 3, then the answer is YES.

If a = 2, b = 11, c = 3, then the answer is NO.

So even with both statements you can't say.

Answer : E
_________________

"Be challenged at EVERY MOMENT."

“Strength doesn’t come from what you can do. It comes from overcoming the things you once thought you couldn’t.”

"Each stage of the journey is crucial to attaining new heights of knowledge."

Rules for posting in verbal forum | Please DO NOT post short answer in your post!

If a,b, and c are prime numbers, do (a+b) and c have a common factor   [#permalink] 14 May 2017, 18:03
Display posts from previous: Sort by

If a,b, and c are prime numbers, do (a+b) and c have a common factor

  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 | 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®.