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

 It is currently 16 Jul 2018, 06:58

### 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

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

# What is the least common multiple of 18,120, 216, and 1080?

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 47015
What is the least common multiple of 18,120, 216, and 1080? [#permalink]

### Show Tags

31 Dec 2017, 14:23
00:00

Difficulty:

25% (medium)

Question Stats:

82% (01:33) correct 18% (03:20) wrong based on 76 sessions

### HideShow timer Statistics

What is the least common multiple of 18,120, 216, and 1080?

A. 1,080
B. 19,440
C. 38,680
D. 38,860
E. 38,880

_________________
examPAL Representative
Joined: 07 Dec 2017
Posts: 500
Re: What is the least common multiple of 18,120, 216, and 1080? [#permalink]

### Show Tags

31 Dec 2017, 14:41
1
Bunuel wrote:
What is the least common multiple of 18,120, 216, and 1080?

A. 1,080
B. 19,440
C. 38,680
D. 38,860
E. 38,880

To answer a question involving least common multiples it is usually helpful to look at prime factorizations.
This is a Precise approach.

18 factors into 3*3*2
120 factors into 12*10 = 2*2*3*5*2
216 factors into 2*108 = 2*3*36 = 2*3*4*9 = (2*2*2)*(3*3*3)
1080 factors into 10*108 = 10*(2*2*2)*(3*3*3)=(2*2*2*2)*(3*3*3)*5

The least common multiple involves the prime factors of all of the above.
Therefore, we need to count the largest number of 2's, 3's and 5's in the above numbers.
1080 has four 2's, 216 and 1080 have three 3's and 120, 1080 have one 5.
Therefore the least common multiple has four 2's, three 3's and one 5.
These are exactly the factors of 1080!
_________________

David
Senior tutor at examPAL
Signup for a free GMAT course

We won some awards:

Save up to \$250 on examPAL packages (special for GMAT Club members)

Manager
Joined: 21 Aug 2017
Posts: 86
Re: What is the least common multiple of 18,120, 216, and 1080? [#permalink]

### Show Tags

15 Feb 2018, 19:27
Is there a quicker way than factoring all of them? Should I have known that those were all factors of 1080?

Maybe I just need to speed up my factoring, but this one took me a touch over 3 minutes.
SVP
Joined: 26 Mar 2013
Posts: 1718
Re: What is the least common multiple of 18,120, 216, and 1080? [#permalink]

### Show Tags

15 Feb 2018, 21:14
jsheppa wrote:
Is there a quicker way than factoring all of them? Should I have known that those were all factors of 1080?

Maybe I just need to speed up my factoring, but this one took me a touch over 3 minutes.

Hi,

If you look carefully to the question, you might find a key or pattern.

1- Look to the above solution, when see number X ends with 0, then make two multiplied numbers, x = 'A * 10'

2- Let's see 1080 = 108 * 10. If you tried to factor 108 I started to divide b 3 so I got 108 = 3 * 36.....So I quickly recognized it is 3 * 6^2. and you can continue.

I detailed process above. However, You need to practice to and hence you will get the skill.
Re: What is the least common multiple of 18,120, 216, and 1080?   [#permalink] 15 Feb 2018, 21:14
Display posts from previous: Sort by

# Events & Promotions

 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®.