As I explain in the video this is a very flexible lesson and you can make the lesson context your own! Don't hesitate to share your personal rationale for the lesson with them prior to the activity. Honesty goes a long ways with kids.
Similar to the other roll out's in this unit, I ask the students to read the problem quietly by themselves and begin formulating a list of Knows and Need to Knows (N2Ks) from the problem. After about 2-3 minutes (since this problem does not have a lot of details to sort through) I ask my students to begin discussing what is "jumping out to them" with their peers. As the students work, they collaborate to create a finalized list of Knows/N2K's with the students sitting around them - - and in the process everyone thoroughly understands what we are looking for in the problem...
THIS IS HALF OF THE BATTLE IN A PROBLEM SOLVING PROBLEM!
(Which is what I will ask the students to reflect on as the culminating piece of the activity.)
Homogeneous groupings work best for this activity because the the students will be able to work at their own pace. It also allows you to focus your efforts on the struggling groups and celebrate "little victories" along the way. Many students will quickly set up and solve the Farmer Bob problem... after this happens, direct them to the 2nd (and then 3rd) entry documents to keep them problem solving and collaborating! This activity practically self-differentiates when run in the manner presented above.
An intervention workshop for struggling students has been provided as an analogous (easier) problem. This helps them to build confidence and make the connection to the real problem at hand. The last remaining point to emphasize is that in the "real" problem the perimeter is not given to the students like it is in the workshop problem (40 cm). The students must carefully look at their list of Knows/N2K's to see that a different piece of information is given: the perimeter of the new pen is TWICE the perimeter of the old. Sometimes this is tough for students to see, but continue to coach them through the problem and celebrate the little victories, no matter how small they may be!
As previously mentioned, when the students begin to finish the first entry document, direct them to the second - and later the 3rd! High ability problem solvers will appreciate the opportunity to see how much they can complete. I even challenge many of my kids to get through all three entry documents, while constantly modeling effective problem solving processes.
Please see the attached video narrative. I encourage you to personalize your questions based on what you have observed in your classroom! Reflection is not a "one size fits all" practice... it is too important and personalized for that!