This lesson provides conceptual practice in all of the measurement formulas needed for 7th grade. It is also great intervention or enrichment for other grade levels. This is conceptual in design because the students quickly see the commonalities in all formulas. It reinforces the idea of variables as "placeholders" and that all formulas are simply algebraic equations in which you must plug in what you know and solve for the unknown. I found this easiest to teach after I've already taught my algebra unit. Also, I've found that this lesson saves a lot of time because once the students understand the concept of formulas and variables, they can apply that knowledge to anything. Great review right before standardized test time!