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

 It is currently 12 Dec 2018, 08:34

# R1 Admission Decisions:

CMU Tepper in Calling R1 Admits   |  Kellogg Calls are Expected Shortly

### 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

## Events & Promotions

###### Events & Promotions in December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
• ### The winning strategy for 700+ on the GMAT

December 13, 2018

December 13, 2018

08:00 AM PST

09:00 AM PST

What people who reach the high 700's do differently? We're going to share insights, tips and strategies from data we collected on over 50,000 students who used examPAL.
• ### GMATbuster's Weekly GMAT Quant Quiz, Tomorrow, Saturday at 9 AM PST

December 14, 2018

December 14, 2018

09:00 AM PST

10:00 AM PST

10 Questions will be posted on the forum and we will post a reply in this Topic with a link to each question. There are prizes for the winners.

# What is the LCM of the numbers 3, a, and 7, if ‘a’ is an integer and a

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

### Hide Tags

e-GMAT Representative
Joined: 04 Jan 2015
Posts: 2291
What is the LCM of the numbers 3, a, and 7, if ‘a’ is an integer and a  [#permalink]

### Show Tags

06 Jun 2018, 21:25
00:00

Difficulty:

65% (hard)

Question Stats:

43% (02:05) correct 58% (02:03) wrong based on 61 sessions

### HideShow timer Statistics

What is the LCM of the numbers 3, a, and 7, if ‘a’ is an integer and a ≥ 3?

Statement 1. ‘a’ is a prime number greater than 2.
Statement 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

Intern
Joined: 15 Jul 2017
Posts: 1
Re: What is the LCM of the numbers 3, a, and 7, if ‘a’ is an integer and a  [#permalink]

### Show Tags

06 Jun 2018, 22:15
Statement 2 is sufficient. Answer Choice B.

Posted from my mobile device
Math Expert
Joined: 02 Aug 2009
Posts: 7102
Re: What is the LCM of the numbers 3, a, and 7, if ‘a’ is an integer and a  [#permalink]

### Show Tags

06 Jun 2018, 22:17
What is the LCM of the numbers 3, a, and 7, if ‘a’ is an integer and a ≥ 3?

Statement 1. ‘a’ is a prime number greater than 2.
a could be 3,5,7... LCM will be different in each case..
Insufficient
Statement 2. Both GCD (3, a) and LCM (3, a) are factors of the number 30.
a can be 3.. both GCD and LCM are 3
a can be 5.. GCD is 1 and LCM is 15, again both factors of 30
Insufficient

Combined..
a can still be 3 or 5
Insufficient

E
_________________

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

Intern
Joined: 21 May 2018
Posts: 2
Re: What is the LCM of the numbers 3, a, and 7, if ‘a’ is an integer and a  [#permalink]

### Show Tags

06 Jun 2018, 22:33
Statement 1 Doesn't help in finding the LCM as a could be either 3 or any other prime. If it is 3 then the LCM is 21 else it is '21a'

Statement 2 By itself is also not sufficient as a could be both 3 or 5. If a is 3 then the LCM of a and 3 is 3 which is a factor of 30, and the GCD is also 3. If a is 5 then LCM is 15 again a factor of 30, and its GCD is 1 which is also a factor.

Both statements together will also not help us to get to the value of a which could be either 3 or 5.

Hence the answer is that both statements taken together are not sufficient.
e-GMAT Representative
Joined: 04 Jan 2015
Posts: 2291
Re: What is the LCM of the numbers 3, a, and 7, if ‘a’ is an integer and a  [#permalink]

### Show Tags

10 Jun 2018, 02:12

Solution

Given:
• a is an integer
• a ≥ 3

To find:
• The LCM of (3, a, 7)

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, LCM (3, a, 7) = LCM (3, 3, 7) = 21
• If a = 5, LCM (3, a, 7) = LCM (3, 5, 7) = 105
• If a = 7, LCM (3, a, 7) = LCM (3, 7, 7) = 21

We can see, for different values of a, we are getting different LCM 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
• If a = 5, GCD (3, a) = GCD (3, 5) = 1 and LCM (3, 5) = 15
o Both 1 and 15 are factors of 30

We can see a can have multiple possible values which satisfy the given statement

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 – 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

Re: What is the LCM of the numbers 3, a, and 7, if ‘a’ is an integer and a &nbs [#permalink] 10 Jun 2018, 02:12
Display posts from previous: Sort by

# What is the LCM of the numbers 3, a, and 7, if ‘a’ is an integer and a

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

 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®.