Overview:  The teacher reviews with students habits and practices for reading maps.  The teacher has students look at the map together, and they point out elements of the map, such as the compass and the legend.  The teacher has students locate their school on the map, and then the teacher asks students to find the grocery store closest to the school.  Students come up with a few different answers, based on which road they would take, whether they would cut across an open field, and whether people are more likely to drive or walk to the store.

Prior knowledge:  The teacher makes a connection with student’s knowledge of the mathematical practice of reading a map.  The teacher reviews basic practices for reading a map, such as paying attention to cardinal directions and locating the legend of the map.  Students indicate that they are quite familiar with the community that the map represents.  When the teacher points out that students will need to use geometry to solve the problem, a student brings up prior knowledge of using constructions, something that is part of the school mathematics knowledge of the class.

Other points of interest:  The teacher and students bring up many different ideas for how students could use the map.  Although the teacher focuses on the mathematical practice of reading the map and paying attention to distances between points, Liza brings up the idea of using constructions.  Although constructions are not a part of the teacher’s launch of the problem, the teacher emphasizes that constructions would be a “wonderful strategy” to solve the problem.  It is not obvious from what we see of this launch whether students recognize the connection between the mathematical practice of reading a map and the school mathematics knowledge of making geometric constructions.