Find all School-related info fast with the new School-Specific MBA Forum

It is currently 24 May 2016, 22:36
GMAT Club Tests

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Problems with LCM & GCD - need help

  post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
VP
VP
User avatar
Joined: 13 Jun 2004
Posts: 1118
Location: London, UK
Schools: Tuck'08
Followers: 7

Kudos [?]: 36 [0], given: 0

Problems with LCM & GCD - need help [#permalink]

Show Tags

New post 05 Sep 2004, 17:12
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Hi,

I'll take the GMAT the 15th of this month, I still have this week to study hard. I know most of the subjects (time/distance, average, time work, triangles, mixture, integer...) But I realize there is something which seems quite simple for everybody but that I can't do it right 100% of the time : LCM or GCD (Least common multiple and greatest common divisor)

I've already looked the lesson in gmat and in the books it's not always very clear. Can someone take 2-3 examples and show me how to find it, especially how to choose the number after you do the prime factorization...

I feel quite stupid to ask this because it seems it's very simple :cry: but I really got a problem there so I hope someone can help. thanks guys.
GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 07 Jul 2004
Posts: 5062
Location: Singapore
Followers: 28

Kudos [?]: 267 [0], given: 0

 [#permalink]

Show Tags

New post 05 Sep 2004, 19:27
LCM = LCM of 2 or more number is the smallest number that can be divided by those 2 or more numbers

E.g. LCM of 4,8 is 8 (not 16, not 32)

2|4,8
2|2,4
2|1,2
|1,1

So LCM = 2*2*2 = 8

8 can be divided evenly by 8
8 can be divided evenly by 4

Another e.g. LCM of 4,8,10

2|4,8,10
2|2,4,5
2|1,2,5
2|1,1,5
5|1,1,1

So LCM = 2*2*2*2*5 = 80


HCF or GCD = HCF of 2 number is the largest number that can be divided evenly into those 2 numbers

E.g. HCF of 4,8

2|4,8
2|2,4
|1,2

So HCF = 2*2 = 4

4 can be divided evenly by 4
8 can be divided evenly by 4 --> Note the difference in wording from LCM

HCF of 4,8,10

2|4,8,10
|2,4,5

So HCF = 2

4 can be divided evenly by 2
8 can be divided evenly by 2
10 can be divided evenly by 2
GMAT Club Legend
GMAT Club Legend
avatar
Joined: 15 Dec 2003
Posts: 4302
Followers: 33

Kudos [?]: 318 [0], given: 0

 [#permalink]

Show Tags

New post 05 Sep 2004, 20:17
In addition, this might be useful:

What is the value of ab?

1. a = 4m, b = 4n, and gcd(m, n) = 1
2. lcm(a, b) = 24

a*b = gcd*lcm
Basically, you would need both 1&2 to answer the question and C would be it. You can test it out with plugging in numbers if you want.
_________________

Best Regards,

Paul

VP
VP
User avatar
Joined: 13 Jun 2004
Posts: 1118
Location: London, UK
Schools: Tuck'08
Followers: 7

Kudos [?]: 36 [0], given: 0

 [#permalink]

Show Tags

New post 05 Sep 2004, 20:55
Thanks you both for your time, your help and your dedication to this forum...I'll let you guys know about my score (good or not) :roll:

This website is amazing and I think now the community is bigger and bigger, I also found a lot of other websites where some people put your link there or talk about Gmat Club...you deserve it !!! :cool
  [#permalink] 05 Sep 2004, 20:55
Display posts from previous: Sort by

Problems with LCM & GCD - need help

  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 and phpBB SEO

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®.