GCF and LCM

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Permalink Reply by Kristin Harding on January 14, 2008 at 4:15pm

Try delicious!

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Permalink Reply by Craig Scribner on January 14, 2008 at 4:25pm

Gina,
Here are some great resources for GCF and LCM:

GCF
http://www.aaamath.com/B/fra66gx2.htm
http://www.brainpop.com/math/problemsolving/greatestcommonfactor/pr... (Here is the Brainpop Video, so you will have to login to view)
http://www.helpwithfractions.com/greatest-common-factor.html

LCM
http://www.math.com/school/subject1/lessons/S1U3L3GL.html
http://www.helpwithfractions.com/least-common-multiple.html
http://www.math.com/school/subject1/practice/S1U3L3/S1U3L3Pract.html
http://amby.com/educate/math/2-1_LCM.html

Enjoy!

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Permalink Reply by Anne Pemberton on January 14, 2008 at 5:25pm

Gina,

Took a few minutes to discern the meaning of LCF and GCF ..... Oh, yeah. that's why kids memorize multiplication facts so that these concepts come easy.

How well do your students kknow their multiplication and division facts? How do they learn best? Are you saying that hands-on and website produce the best results. What methods have you already tried or are currently using?

I have some materials online that may be useful although they are not directed for these concepts. You can look over the multiplication and division materials on http://www.educationalsynthesis.org/mrsp/math .

It may be useful for the students to use manipulatives, graph paper, or rows of dots, and see how many sets they can make of a number of units. Look at the Draw and Multiply or Draw and Divide worksheets on the above site, and see if they will be of any help.

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Permalink Reply by Arlene Anderson on January 14, 2008 at 5:58pm

Gina,
Have you ever heard of the cake method? It's a great lesson on GCF and LCM and once students do it, they will never forget how to find their answer. I use it with either an interactive white board or Interwrite pad where all students can get involved.
To start you pick two numbers - let's say 24 and 36. I've done a little picture in paint (sorry my Mac is at school) to show the process. You can discuss how 24 and 36 are both even, therefore, divisible by 2. Draw a line under the 2 initial numbers and put the division answers below the line. Place a 2 to the left of the two numbers. Continue in this way until you have only prime numbers. In this case 2 and 3. Draw and L shape around the side and bottom numbers (LCM) and if you only circle the side numbers you have the GCF.
Like I said this works great with an interactive board or pad.
I hope this helps.

Attachments:

• LCM GCF.JPG, 28 KB

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