To begin with, I read on Math Goodies a neat way to explain it linking it to perimeter and area. The way I am going to explain it to my students is building a garden If I said I wanted a garden with 5 sq. ft. the dimensions can only be 1 ft. + 1 ft. + 5 ft. + 5 ft. , and the area would be 5 sq. ft. This is the ONLY way to build the garden to those specifications.
|Stress that this being the only way makes it prime!!|
|More than one way to build make is composite!!|