This is actually a very smart idea to use in lower elementary to find the greatest common factor as well as the lowest common multiple because when the students get into the higher mathematics when they start learning about the Venn Diagram. However, this could go from being an aid to becoming a crutch for the students.
Free download! 40 Task Cards for Greatest Common Factor. This product is printer friendly. No clip art or heavy borders requiring lots of ink! 4 cards per page. Includes answer key and printable answer recording sheet for students.