Joe and Maria are 5th graders. Joe is two inches taller than Maria.
I asked the students to put this information into a function table and give me some measurements for Joe and Maria. I reminded them to make them reasonable measurements for 5th grade students. Of course, everyone had different answers, and all were acceptable as long as Joe was two inches taller. Next, I recorded some of their measurements on the board and asked them to explain how they came up with Joe's height. We also noticed that our function table was similar to the In and Out boxes they have become so familiar with using Everyday Math. I asked them what the rule was for this table. Of course, they all said "add 2!" Then, I encouraged them to tell me the rule for finding Joe's height based on Maria's if we use m for Maria. This was a little tricker, but with a little prompting, they said "m+2!" Now we're talking!
Next, we wrote some sample problems in our notebooks and came up with expressions to describe the problems (EDM 10.3):
After some more practice independently, I gave the students an opportunity to write their own problem situations that would require the use of a variable. I forgot to capture this in a photo, but they did a really great job! Being able to write their own, and accurately, made me feel confident in their understanding of expressions.