GCF Foldable – 4 Methods

The GCF foldable and videos below show four methods that you can use to find the G.C.F. (greatest common factor).  See the steps and examples that I chose for the GCF foldable below.


Method 1:  Make a List

Steps:

1.  List all factors for both numbers.

2.  Identify all common factors.

3.  Select the biggest factor that both numbers share.

Examples:

A.        12 and 36
GCF Foldable

B.        18 and 45

GCF Foldable


Method 2:  Prime Factorization

Steps:

1.  Find the prime factorization of both numbers.

2.  Compare the prime factorizations:  circle common prime factors.

3.  Multiply the common prime numbers.

Examples:

A.        30 and 16
GCF Foldable

B.        75 and 90

GCF Foldable


 

 

Method 3:  Venn Diagram

Steps:

1.  Find the prime factorization of both numbers.

2.  Fill out the Venn diagram.  Put the common prime numbers in the middle first.

3.  Multiply the common prime numbers from the middle of the Venn diagram.

Example:

GCF Foldable

 Video:


Method 4:  Ladder (Upside Down Division)

Steps:

1. Divide both numbers by the smallest prime number possible.

2. Continue the process until one or both numbers (on the inside) cannot be simplified any further.

3.  Multiply the prime numbers that you divided by.  (The numbers on the left.)

Examples:

A.        40 and 32

GCF Foldable

 

 

 

B.        12 and 18

GCF Foldable

Video:


GCF Foldable

I created this foldable using cardstock so that I could use my flair pens without them bleeding through the paper.

GCF Foldable Outside:

GCF Foldable

GCF Foldable Inside:

GCF Foldable

GCF Foldable – Two Flaps Open:

GCF Foldable

GCF Foldable – Two Flaps Open:

GCF Foldable

Do you know of any other methods that I should try?  Are there any of these methods that you have never tried before?

Coming Soon:  Would you prefer to buy the computer version?  Get it here (coming soon)!

GCF Foldable

Divisibility Rules Poster Options

I am working on converting old anchor charts and notes to typed posters.

Divisibility Rules Poster Options:

Color:

Slide1

Black and White:

Slide2

Use these photos as a poster to display in your classroom, or print for use in student notebooks/binders.  Here is the FREE .pdf:  DivisibilityRulesPoster.

So, what is this trick for the 7’s divisibility rules?  

Check it out:

  • Double the last digit and subtract it from the remaining part of the number.  If the answer is either 0 or it is divisible by 7, then the original number is divisible by 7.

Example:

  • Start with the number:  1015.
  • Isolate the last digit:  1015 .
  1. Double the last digit.  5 x 2 = 10.
  2. Subtract the result (10) from the remaining part of the number (101):  101 – 10 = 91
  3. Determine whether your answer is equal to 0 or divisible by 7.  If it is, the number is divisible by 7.  If it is not, the number is not divisible by 7.
  • 91 divided by 7 equals 13, which is a whole number.
  • Since 91 is divisible by 7, that means 1015 is also divisible by 7.
  • If you are curious, and don’t feel like working it out… 1015 divided by 7 equals 145.

It is probably easier just to do long division in most cases, but it is always fun to learn a new trick 😉

Check out my post on making a divisibility rules foldable.

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