Overview:  As students enter the classroom, the teacher passes out a survey for students to collect data about students’ shopping habits.  The survey provides students with a list of grocery stores in their community and asks students to mark which store they shop at most often.  When looking at the results of the survey, students note that very few people in the class shop at the grocery stores in Sycamore, and many people shop in Chesterton.  Students in the class share some of the reasons that they or their families choose to shop at certain stores instead of others.  The teacher tells students that, with all of this information in mind, they will need to work on a problem to determine the best location in town for a new grocery store.  The teacher tells students that, instead of considering all of the complexity of the many different grocery stores in town, they will consider an area with only three existing grocery stores.

Prior knowledge:  The teacher makes a connection with students’ knowledge of the context of the problem.  The teacher connects with students’ experiences outside of school by giving them time to share the different choices they make about buying groceries.  By giving out the survey and sharing the results with students, the teacher attempts to help students start thinking about what areas of the community are most often visited by students in the class.  With his final comments, the teacher begins to make a connection with students’ prior knowledge of school mathematics.  After considering the contextual factors of the problem, the teacher tells students that they will simplify the problem so that they can locate a new store that is equidistant from three existing stores.  By introducing formal geometric language during the launch, the teacher may be provoking students to shift from considering the contextual elements of the problem to relying on their prior knowledge of geometry.

Other points of interest:  In the teacher’s final comments to students in this launch, the teacher tells students that “we want a geometric strategy.”  After investing time hearing about students’ shopping experiences and choices, the teacher may de-value students’ experiences in favor of finding a solution that would be appropriate for a geometry class.  After considering all of the complexity of the problem as a class, the teacher urges students to simplify the contextual elements of the problem.  The teacher also uses the language of “we” to describe what students in the class need to do: “we want a geometric strategy,” and “we’re going to simplify the problem.”  The use of the pronoun “we” in mathematics classrooms is vague in regards to whom it refers (Pimm, 1987), but the pronoun may be a strategy to draw students into the work (Herbel-Eisenmann & Wagner, 2007).