This opening lesson invites students to experiment with expressions and equations to model a situation. Students think about relevant quantities, whether they might be fixed or variable, and how they might relate to one another. They make assumptions and estimates, and use numbers and letters to represent the quantities and relationships. The lesson also draws attention to the idea of constraints and how to represent them. 

There is not one correct set of expressions or equations governing the potential quantities involved in the situation. The focus is on the modeling process itself—identifying relevant quantities, making assumptions, creating a model, and evaluating the model (MP4).

Making internet-enabled devices available gives students an opportunity to choose appropriate tools strategically (MP5).