The goal for this number talk is to see how this connects with the content that students in K to 2 are learning.

Step 1: Brainstorm Strategies

Without talking, writing, or counting squares one-by-one, figure out how many unit squares are on the border of the 10 x 10 square pictured below. Take a few minutes to think of multiple strategies to solve problem.

A ten by ten square grid is shown. The smaller unit squares along the border of the large square are shaded grey.

Step 2: Record answers and strategies

Designate one person as the recorder (teacher).
Share all possible answers with the PLC, as the recorder writes each one without revealing the correct answer.
Take turns sharing your strategies with the group, while the recorder diagrams each strategy along with the "student’s" name.

Example Recording

Watch Cathy Humphreys lead this problem with her 7th grade students. As you watch, pay special attention to how Cathy records student thinking and how she elicits student ideas.

(Caption File)

Cammisuli, Meredith. "Border Problem Part 1." YouTube. YouTube, 27 Nov. 2013. Web. 12 July 2016.

Discussion Questions

After watching the video, discuss the following questions in your PLC:

What are your initial reactions to this lesson?
What strategies did the students use to solve the border problem, and how were they similar or different to the strategies you used in your group?
What connections did you notice among the strategies?
What did you notice about how Cathy recorded student strategies?