Overview:  Jamal, Rashid, Sophie, and Mariana are working together.  First, the students decide they should place a new store south of Calumet Drive, because people in Sycamore currently have few shopping options.  After they decide on a point, Mariana points out that they need to have a geometric solution to the problem.  Working together, the students direct Rashid to measure 1-inch each from points D and E.  Sophie suggests he angle the line segments towards one another to make approximately an isosceles triangle, which Mariana refers to as an equilateral triangle.  The new vertex is what students determine should be the new grocery store.

Prior knowledge:  The students first use their prior knowledge of the context of the problem, when they decide that they should locate a store in an area where there are currently very few grocery stores.  Because they remember that they need to establish a geometric solution to the problem, the students rely more on their prior knowledge of school mathematics.  Recognizing that 1 inch on the map represents two miles, the students measure 1 inch from the two points on the map in the region they have decided to locate a new store.  The students make a triangle whose third vertex will be the location of the new grocery store.

Other points of interest:  Although Mariana suggests that the students have constructed an equilateral triangle, they actually make only an approximation of an isosceles triangle.  The students assumed that the vertices given by points D and E would be the vertices of an isosceles triangle with equal sides of length 1 inch.  However, this is not necessarily the case, and Rashid only approximates the angles of the triangle, which likely changes the lengths of the sides.  At the end, the students reconcile their geometric solution with their initial desire to locate a new grocery store in Sycamore.