Facebook Focus: Rate of Change

Today, a student in my Algebra class was confused about what rate of change was and how to calculate the rate of change given the measurements for two quantities. The problem she had was:

Rather than respond directly to her e-mail I posted the following general response to our FB group. My response was:

This comment was also posted to my IB Math SL class that is about to begin an introduction of calculus. A very useful 10 minutes spent discussing a very important concept with two of my classes via FB. We'll see what type of student comments are generated, either in class tomorrow or later tonight online.