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

 It is currently 20 Sep 2018, 17:21

### 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 Greatest Common Factor (GCF) of 18x^8y^20 and 24x^12y^15?

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 49271
What is the Greatest Common Factor (GCF) of 18x^8y^20 and 24x^12y^15?  [#permalink]

### Show Tags

21 Aug 2018, 06:36
00:00

Difficulty:

15% (low)

Question Stats:

80% (00:48) correct 20% (00:31) wrong based on 49 sessions

### HideShow timer Statistics

What is the Greatest Common Factor (GCF) of $$18x^8y^{20}$$ and $$24x^{12}y^{15}$$?

A. $$3x^4y^5$$

B. $$6x^4y^5$$

C. $$3x^8y^{15}$$

D. $$6x^8y^{15}$$

E. $$72^{12}y^{20}$$

_________________
Manager
Joined: 18 Jul 2018
Posts: 191
Location: India
Concentration: Finance, Marketing
WE: Engineering (Energy and Utilities)
Re: What is the Greatest Common Factor (GCF) of 18x^8y^20 and 24x^12y^15?  [#permalink]

### Show Tags

21 Aug 2018, 06:41
1
Prime factorizing 18 and 24 gives
18 = 2*$$3^2$$
24 = $$2^3$$*3
GCF of 18 and 24 is 6
Again GCF of $$x^8$$$$y^{20}$$ and $$x^{12}$$$$y^{15}$$ is $$x^8$$$$y^{15}$$

GCF is 6$$x^8$$$$y^{15}$$

BSchool Forum Moderator
Joined: 26 Feb 2016
Posts: 3131
Location: India
GPA: 3.12
Re: What is the Greatest Common Factor (GCF) of 18x^8y^20 and 24x^12y^15?  [#permalink]

### Show Tags

21 Aug 2018, 06:43
Bunuel wrote:
What is the Greatest Common Factor (GCF) of $$18x^8y^{20}$$ and $$24x^{12}y^{15}$$?

A. $$3x^4y^5$$

B. $$6x^4y^5$$

C. $$3x^8y^{15}$$

D. $$6x^8y^{15}$$

E. $$72^{12}y^{20}$$

The greatest common factor of $$18x^8y^{20}$$ and $$24x^{12}y^{15}$$ can be found out as follows:

We can also write $$18x^8y^{20}$$ as $$3*6*x^8*y^{15}*y^5$$
Similarly, we can write $$24x^{12}y^{15}$$ as $$4*6*x^{8}*x^4*y^{15}$$

This follows the general rule of exponents which is $$a^{m+n} = a^m*a^n$$

Therefore, the greatest common factor(GCF) of $$18x^8y^{20}$$ and $$24x^{12}y^{15}$$ is $$6*x^8*y^{15}$$(Option D)
_________________

You've got what it takes, but it will take everything you've got

PS Forum Moderator
Joined: 25 Feb 2013
Posts: 1212
Location: India
GPA: 3.82
Re: What is the Greatest Common Factor (GCF) of 18x^8y^20 and 24x^12y^15?  [#permalink]

### Show Tags

21 Aug 2018, 06:43
Bunuel wrote:
What is the Greatest Common Factor (GCF) of $$18x^8y^{20}$$ and $$24x^{12}y^{15}$$?

A. $$3x^4y^5$$

B. $$6x^4y^5$$

C. $$3x^8y^{15}$$

D. $$6x^8y^{15}$$

E. $$72^{12}y^{20}$$

$$18x^8y^{20}=2*3^2x^8y^{20}$$

$$24x^{12}y^{15}=2^3*3x^{12}y^{15}$$

Therefore $$GCD = 2*3x^8*y^{15}$$, for GCD pick the lowest powers of $$x$$ & $$y$$

Option D
Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4031
Location: India
GPA: 3.5
Re: What is the Greatest Common Factor (GCF) of 18x^8y^20 and 24x^12y^15?  [#permalink]

### Show Tags

21 Aug 2018, 07:27
Bunuel wrote:
What is the Greatest Common Factor (GCF) of $$18x^8y^{20}$$ and $$24x^{12}y^{15}$$?

A. $$3x^4y^5$$

B. $$6x^4y^5$$

C. $$3x^8y^{15}$$

D. $$6x^8y^{15}$$

E. $$72^{12}y^{20}$$

Just find the common term only 10 sec required....

Common factor of $$18x^8y^{20}$$ ,$$24x^{12}y^{15}$$

= $$6x^8y^{15} ( 3y^5 , 4x^4)$$

_________________

Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )

SVP
Joined: 26 Mar 2013
Posts: 1808
Re: What is the Greatest Common Factor (GCF) of 18x^8y^20 and 24x^12y^15?  [#permalink]

### Show Tags

22 Aug 2018, 05:50
Bunuel wrote:
What is the Greatest Common Factor (GCF) of $$18x^8y^{20}$$ and $$24x^{12}y^{15}$$?

A. $$3x^4y^5$$

B. $$6x^4y^5$$

C. $$3x^8y^{15}$$

D. $$6x^8y^{15}$$

E. $$72^{12}y^{20}$$

GFC of 18 & 24 = 6.........Eliminate choices A, C & E

GFC of $$x^8$$ and $$x^{12}$$ = $$x^8$$.....Eliminate B

Re: What is the Greatest Common Factor (GCF) of 18x^8y^20 and 24x^12y^15? &nbs [#permalink] 22 Aug 2018, 05:50
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®.