A Venn Diagram is a powerful visual way to show the factors of a number, and the common factors of two numbers. Nice implementation.

Here is the home page for this activity
http://www.teacherled.com/2009/01/31/venn-factors/

The learning activity can be found at:
http://www.teacherled.com/resources/vennfactors/vennfactorload.html

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Here are the comparable Venn Diagram resources for multiples:

Home page
http://www.teacherled.com/2009/01/27/venn-multiples/

And the learning resource
http://www.teacherled.com/resources/vennmultiples/vennmultipleload.html