Education Technology

It's Greek to Me

Activity Overview

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
  • Re-teach concepts as necessary