# 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

B.        18 and 45

# 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

B.        75 and 90

# 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.

# 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

B.        12 and 18

# GCF Foldable

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

## GCF Foldable – Two Flaps Open:

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)!

# Divisibility Rules Poster Options

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

# Divisibility Rules Poster Options:

## Black and White:

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: