Students learn Euclid's Method of finding the Greatest Common Factor of large numbers. They also review finding GCF using prime factorization and listing.

Before the Activity

See the attached PDF file for detailed instructions for this activity

Print pages 39 - 42 from the attached PDF file for your class

During the Activity

Distribute the pages to the class.

Follow the Activity procedures:
Method 1

Use the Euclid method and the integer divide function on the calculator to find the GCF of the two given numbers

Divide the larger number by the smaller number

Successively divide the larger number by the smaller number until the remainder is zero

GCD is the last divisor

Method 2

Write the two numbers as a product of prime factors

Find the factors common to both and multiply them to get the GCF

Method 3

List all the factors for both the numbers

Find the greatest factor (divisor) common to both, which is the GCF

Method 4

Use the GCD function on the calculator find the GCD of the two numbers

After the Activity

Students will complete the Worksheet and analyze the results.

Review student results:

As a class, discuss questions that appeared to be more challenging