The problem given above is a real-world representation of a linear function. Students are next asked to generate a table of values that show the relationship between age and median weight for the first six months of age and enter this information in the graphing calculator. Figure A is the display of a Texas Instruments TI-83 graphing calculator after a student has entered the data. The L1 column is the ages in months and the L2 column is the median weight for girls in pounds. The horizontal axis is the ages in months and the vertical axis is the median weight in pounds.
Most students notice that the dots lie in a straight line.
Many students make sense of this by either referring to the table or the real-world situation. The comments that students make during this part of the lesson are typically about the translations between representations rather than of the representations themselves. Students are also explaining their reasoning to other students and to the teacher. The next part of the activity is where the use of a graphing calculator is essential. The goal for the students is to change the values of the m and b so that the line passes through all the points on the scatter-plot.