The central idea of teaching with variation is to highlight the essential features of a concept or idea through varying the non-essential features 

Variation is not the same as variety – careful attention needs to be paid to what aspects are being varied (and what is not being varied) and for what purpose.

NCETM The 5 Big Ideas of Teaching for Mastery

Procedural variation provides the opportunity

Intelligent Practice

When constructing a set of activities or questions it is important to consider what connects the examples; what mathematical structures are being highlighted?

Students are encouraged to avoid mechanical practice and, instead, to practice the thinking process (intelligent practice)

Research suggests that mathematical thinking occurs when students are thinking about mathematical structure.

Conceptual Variation

Multiple Representations

Carefully planned variation reveals mathematical structure.