The formula for the variance of a binomial distribution is both concise and elegant. However, it is often taught without reference to the underlying reasoning. That being the case, is it important, or useful, to understand why this formula can be used to calculate the requisite result? In this article, the author demonstrates a teaching sequence that foregrounds the reasoning behind the formula. Implications for teaching are discussed, including the placement of this learning in the context of practising other valued skills.