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

It is currently 23 Jan 2019, 23:34

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 in January
PrevNext
SuMoTuWeThFrSa
303112345
6789101112
13141516171819
20212223242526
272829303112
Open Detailed Calendar
  • Key Strategies to Master GMAT SC

     January 26, 2019

     January 26, 2019

     07:00 AM PST

     09:00 AM PST

    Attend this webinar to learn how to leverage Meaning and Logic to solve the most challenging Sentence Correction Questions.
  • Free GMAT Number Properties Webinar

     January 27, 2019

     January 27, 2019

     07:00 AM PST

     09:00 AM PST

    Attend this webinar to learn a structured approach to solve 700+ Number Properties question in less than 2 minutes.

What is the GCD of the numbers 3, a, and 12, if ‘a’ is an integer

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

Hide Tags

 
e-GMAT Representative
User avatar
D
Joined: 04 Jan 2015
Posts: 2466
What is the GCD of the numbers 3, a, and 12, if ‘a’ is an integer  [#permalink]

Show Tags

New post 07 Jun 2018, 21:44
00:00
A
B
C
D
E

Difficulty:

  85% (hard)

Question Stats:

47% (02:12) correct 53% (02:04) wrong based on 87 sessions

HideShow timer Statistics

What is the GCD of the numbers 3, a, and 12, if ‘a’ is an integer and a ≥ 3?

    1. ‘a’ is a prime number greater than 2.
    2. Both GCD (3, a) and LCM (3, a) are factors of the number 30.

_________________








Register for free sessions
Number Properties | Algebra |Quant Workshop

Success Stories
Guillermo's Success Story | Carrie's Success Story

Ace GMAT quant
Articles and Question to reach Q51 | Question of the week

Must Read Articles
Number Properties – Even Odd | LCM GCD | Statistics-1 | Statistics-2 | Remainders-1 | Remainders-2
Word Problems – Percentage 1 | Percentage 2 | Time and Work 1 | Time and Work 2 | Time, Speed and Distance 1 | Time, Speed and Distance 2
Advanced Topics- Permutation and Combination 1 | Permutation and Combination 2 | Permutation and Combination 3 | Probability
Geometry- Triangles 1 | Triangles 2 | Triangles 3 | Common Mistakes in Geometry
Algebra- Wavy line | Inequalities

Practice Questions
Number Properties 1 | Number Properties 2 | Algebra 1 | Geometry | Prime Numbers | Absolute value equations | Sets



| '4 out of Top 5' Instructors on gmatclub | 70 point improvement guarantee | www.e-gmat.com

Manager
Manager
avatar
B
Joined: 22 Sep 2017
Posts: 170
Re: What is the GCD of the numbers 3, a, and 12, if ‘a’ is an integer  [#permalink]

Show Tags

New post 08 Jun 2018, 07:25
EgmatQuantExpert wrote:
What is the GCD of the numbers 3, a, and 12, if ‘a’ is an integer and a ≥ 3?

    1. ‘a’ is a prime number greater than 2.
    2. Both GCD (3, a) and LCM (3, a) are factors of the number 30.



Option-1 - "a" can have any number greater than or equal to 3. So we can't determine the exact GCD(3,a,12). Insufficient.
Option-2 - Here "a" can have values such as 5, 6 and 10. In all cases GCD(3,a) and LCM(3,a) are factors of 30. So we can't derive exact value of GCD(3,a,12). Insufficient.

Now, combining both options we will have only one value of "a=5" as 5 is the only prime number greater than 2. So we can find out the exact value of GCD now.
So, the answer is C.
Intern
Intern
avatar
B
Status: Rise above
Joined: 20 Feb 2017
Posts: 46
Location: India
Schools: ESSEC '22
GMAT 1: 650 Q47 V34
GPA: 3
WE: Editorial and Writing (Entertainment and Sports)
What is the GCD of the numbers 3, a, and 12, if ‘a’ is an integer  [#permalink]

Show Tags

New post 08 Jun 2018, 21:17
jackspire wrote:
EgmatQuantExpert wrote:
What is the GCD of the numbers 3, a, and 12, if ‘a’ is an integer and a ≥ 3?

    1. ‘a’ is a prime number greater than 2.
    2. Both GCD (3, a) and LCM (3, a) are factors of the number 30.



Option-1 - "a" can have any number greater than or equal to 3. So we can't determine the exact GCD(3,a,12). Insufficient.
Option-2 - Here "a" can have values such as 5, 6 and 10. In all cases GCD(3,a) and LCM(3,a) are factors of 30. So we can't derive exact value of GCD(3,a,12). Insufficient.

Now, combining both options we will have only one value of "a=5" as 5 is the only prime number greater than 2. So we can find out the exact value of GCD now.
So, the answer is C.

What if we consider a=3? then GCD of (3,3) =3 and LCm of (3,3) =3 which is a factor of 30. Hence answer should be E in my opinion.
e-GMAT Representative
User avatar
D
Joined: 04 Jan 2015
Posts: 2466
Re: What is the GCD of the numbers 3, a, and 12, if ‘a’ is an integer  [#permalink]

Show Tags

New post 11 Jun 2018, 05:22

Solution



Given:
    • a is an integer
    • a ≥ 3

To find:
    • The GCD of (3, a, 12)

Analysing Statement 1
    • As per the information given in statement 1, ‘a’ is a prime number greater than 2
      o Therefore, ‘a’ can have values like 3, 5, 7, 11 etc

    • If a = 3, GCD (3, a, 12) = GCD (3, 3, 12) = 3
    • If a = 5, GCD (3, a, 12) = GCD (3, 5, 12) = 1
    • If a = 7, GCD (3, a, 12) = GCD (3, 7, 12) = 1

We can see, for different values of a, we are getting different GCD values

Hence, statement 1 is not sufficient to answer

Analysing Statement 2
    • As per the information given in statement 2, both GCD (3, a) and LCM (3, a) are factors of the number 30
      o Factors of 30 = 1, 2, 3, 5, 6, 10, 15, and 30

    • If a = 3, GCD (3, a) = GCD (3, 3) = 1 and LCM (3, 3) = 3
      o Both 1 and 3 are factors of 30
      o Also, GCD (3, a, 12) = GCD (3, 3, 12) = 3

    • If a = 5, GCD (3, a) = GCD (3, 5) = 1 and LCM (3, 5) = 15
      o Both 1 and 15 are factors of 30
      o Also, (3, a, 12) = GCD (3, 5, 12) = 1

We can see a can have multiple possible values which satisfy the given statement, and the GCD of (3, a, 12) is different for different values of a

Hence, statement 2 is not sufficient to answer

Combining Both Statements
Even after combining the statements, we can say
    • a can be 3 or 5, for which GCD is different – hence unique value of a cannot be determined

Hence, the correct answer is option E.

Answer: E
_________________








Register for free sessions
Number Properties | Algebra |Quant Workshop

Success Stories
Guillermo's Success Story | Carrie's Success Story

Ace GMAT quant
Articles and Question to reach Q51 | Question of the week

Must Read Articles
Number Properties – Even Odd | LCM GCD | Statistics-1 | Statistics-2 | Remainders-1 | Remainders-2
Word Problems – Percentage 1 | Percentage 2 | Time and Work 1 | Time and Work 2 | Time, Speed and Distance 1 | Time, Speed and Distance 2
Advanced Topics- Permutation and Combination 1 | Permutation and Combination 2 | Permutation and Combination 3 | Probability
Geometry- Triangles 1 | Triangles 2 | Triangles 3 | Common Mistakes in Geometry
Algebra- Wavy line | Inequalities

Practice Questions
Number Properties 1 | Number Properties 2 | Algebra 1 | Geometry | Prime Numbers | Absolute value equations | Sets



| '4 out of Top 5' Instructors on gmatclub | 70 point improvement guarantee | www.e-gmat.com

Manager
Manager
avatar
G
Joined: 30 Mar 2017
Posts: 134
GMAT 1: 200 Q1 V1
Reviews Badge
Re: What is the GCD of the numbers 3, a, and 12, if ‘a’ is an integer  [#permalink]

Show Tags

New post 23 Jun 2018, 11:40
What is the GCD of 3,a,12, where a ≥ 3? This is the same as what is the GCD of 3 and a?
If a is a multiple of 3, answer will be 3. If a is not a multiple of 3, answer will be 1.

(1)
a is a prime greater than 2.
If a=3, GCD=3
If a=5, GCD=1
Not suff

(2)
a=3 and a=5 also fit here.

Answer: E
GMAT Club Bot
Re: What is the GCD of the numbers 3, a, and 12, if ‘a’ is an integer &nbs [#permalink] 23 Jun 2018, 11:40
Display posts from previous: Sort by

What is the GCD of the numbers 3, a, and 12, if ‘a’ is an integer

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


Copyright

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®.