This article provides a task that can be used effectively for exploring arrays in middle and upper primary schools, and the notion of prime and composite numbers in particular. As students are engaging in these activities, teachers can encourage them to record their arrays both diagrammatically and as number sentences.

Regular contributors James and Toby Russo return with a sixth principle for educationally-rich mathematical games--almost all mathematical games have the potential to be transformed into an investigation. This article builds on their earlier piece with Leicha A Bragg (APMC 23(3), 30-34). [For "Five Principles of Educationally Rich…