Education Technology

It's Greek to Me

Published on 06/09/2008

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