Help please---Greatest Common Factor - ProTeacher Community




Home Join Now Search My Favorites
Help


      Intermediate Grades (3-5)

Help please---Greatest Common Factor

>

Reply
 
Thread Tools
catapult catapult is offline
 
Joined: Nov 2011
Posts: 95
Full Member

catapult
 
Joined: Nov 2011
Posts: 95
Full Member
Help please---Greatest Common Factor
Old 01-25-2013, 12:10 PM
 
Clip to ScrapBook #1

any ideas for how to teach GCF... I have never taught it yet- and I want my kids to understand it well... (also how do I explain to my students what factors are- in a clear way?)


catapult is offline   Reply With Quote

Phyllis's Avatar
Phyllis Phyllis is offline
 
Joined: Aug 2005
Posts: 3,383
Senior Member

Phyllis
 
Phyllis's Avatar
 
Joined: Aug 2005
Posts: 3,383
Senior Member
Finding the greatest common factor
Old 01-25-2013, 05:05 PM
 
Clip to ScrapBook #2

Just like addends are the numbers you add together to get a sum, factors are the numbers you can multiply together to get a product. Every number has at least two factors: the number itself and one:

7: 1, 7 Numbers with only those two factors are called prime numbers. 3, 5, 7, 11, 13, 17, 19 are some prime numbers.

Some examples of numbers with more factors:
12: 1, 2, 3,4,6, 12
20: 1, 2, 4, 5, 10, 20
15: 1, 3, 5, 15

I would do many examples like these on the board and then give them some examples to do on their own:

8: __ __ __ __
36: __ __ __ __ __ __ __ __ __

After they have shown that they can do this, it's time to give them some numbers to find the largest common multiple for.

9: 1, 3, 9
15: 1, 3, 5, 15
3 is the largest common multiple

28: __ __ __ __ __ __
42: __ __ __ __ __ __ __ __ This is a good example of another
they could be given.
Phyllis is offline   Reply With Quote
DaisyLilli DaisyLilli is offline
 
Joined: Jun 2008
Posts: 887
Senior Member

DaisyLilli
 
Joined: Jun 2008
Posts: 887
Senior Member

Old 01-26-2013, 08:16 PM
 
Clip to ScrapBook #3

We used factor rainbows...hard to explain, but google and it will give you pictures and explainations. We would make a rainbow for each number (like 12 and 32) and then circle all the numbers that were the same (factors) and then put a star on the gcf.

It was great for different types of learners since it could be easily color-coded if needed.
DaisyLilli is offline   Reply With Quote
Linda/OH's Avatar
Linda/OH Linda/OH is offline
 
Joined: Aug 2007
Posts: 5,515
Senior Member

Linda/OH
 
Linda/OH's Avatar
 
Joined: Aug 2007
Posts: 5,515
Senior Member
factor rainbows
Old 01-27-2013, 04:51 AM
 
Clip to ScrapBook #4

I just googled it and find it very cool! I tried out a few to see how to make them and what they'll look like.

Question: what happens to single numbers that don't connect to another number as in the case of 10 as a factor of 100? or 3 as a factor of 9?
Linda/OH is offline   Reply With Quote
Linda/OH's Avatar
Linda/OH Linda/OH is offline
 
Joined: Aug 2007
Posts: 5,515
Senior Member

Linda/OH
 
Linda/OH's Avatar
 
Joined: Aug 2007
Posts: 5,515
Senior Member
factor rainbow picture
Old 01-27-2013, 12:42 PM
 
Clip to ScrapBook #5

I found my own answer:
http://edtech2.boisestate.edu/brianr...torrainbow.jpg


Linda/OH is offline   Reply With Quote

Join the conversation! Post as a guest or become a member today. New members welcome!

Reply

 

>
Intermediate Grades (3-5)
Thread Tools




Sign Up Now

Sign Up FREE | ProTeacher Help | BusyBoard

All times are GMT -8. The time now is 01:14 AM.

Copyright © 2019 ProTeacher®
For individual use only. Do not copy, reproduce or transmit.
source: www.proteacher.net