How to Find the Greatest Common Factor

Expand the description and view the text of the steps for this how-to video.

Check out Howcast for other do-it-yourself videos from stevenkittinger and more videos in the Mathematics Tests category.

You can contribute too! Create your own DIY guide at http://www.howcast.com/videos/new or produce your own Howcast spots with the Howcast Filmmakers Program at http://www.howcast.com/filmmakers/apply.

The methods for finding the greatest common factor for a series of numbers and for an algebraic expression are similar.

To complete this How-To you will need:

A series of numbers
Algebraic expressions

Step 1: Determine for a series of numbers

Factor each number in a series of numbers completely into its primes; identify the common factors for each number; and then multiply the common factors together.

Tip: A prime number is a positive integer that is not itself the product of two smaller positive integers.

Step 2: Use 18 and 27

Use the numbers 18 and 27 as an example. The primes of 18 are three, three, and two. The primes of 27 are three, three, and three. So the greatest common factor is three times three, or nine.

Step 3: Determine the greatest common factor for algebraic expressions

Identify all of the common factors in a series of algebraic expressions.

Step 4: factor 60x2y and 210xy2

Use the expressions the common factors of the first expression are two, two, three, five, x, x, and y. The common factors in the second expression are two, three, five, seven, x, y, and y. So the greatest common factor is two times three times five times x times y, or 30xy.

Thanks for watching How To Find the Greatest Common Factor! If you enjoyed this video subscribe to the Howcast YouTube channel! http://www.youtube.com/subscription_center?add_user=howcast

Category:

Howto & Style

Tags:

• HotHowTos
• finding
• calculating
• greatest
• common
• factor
• mathematics
• studying
• test
• exam

[adidasx311]

there is a wayyy wayyy wayy easier way to do this.

its called a factor tree.

[MichaelOusstrin]

stop doing math vids...kids have teachers for that

[VipeBoogie]

french

to fancy 

[Debedeb]

this is too fast and gives a student no time to soak anyting in ... it sounds like this, "factor,12##%#$## times x times y @#$#@ 234324 or 882828 @#$#@$@$" ;D thanks for sharing anyways

[WebkinzAnimania43]

Ur doin' it wrong..

[freezingcold1]

BORING!

[abecrombie52]

@MichaelOusstrin if u think that why are u looking at ths vid???

[barbieandbratz4ever6]

lolz are you all kids or high schools !

[barbieandbratz4ever6]

@adidasx311 i know how i will get on a vid of that goooooood lucky

[2015fifa]

@MichaelOusstrin the fuck up men shut up

[youlovemathematics]

If you want to become good at math go to my youtube channel: (Youlovemathematics).In my channel i will teach you everything about math step by step. I will start with teaching you (necessary basic math skills) and then I will teach you the more advanced math topics. Just click on Playlists when you are on my channel and you will be able to watch my math videos in order. I promise that i will teach everything in an easy way. Math is easy if you have a good teacher.

youlovemathematics

[13Haylz]

At first I got comfused with the GCF..now im just comfused with the alberia expression n stuff..math was SO much easier until they put letters in math -_-