This lesson is optional because it is an opportunity for extra practice with addition and subtraction within 100 that not all classes may need. In the first activity, students learn Stage 5 of the Target Numbers center. In this new stage, called Subtract Two-Digit Numbers, students roll number cubes to create two-digit numbers to subtract from a starting number to get as close to 0 as possible. In the second activity, students can chose to continue working on Subtract Two-Digit Numbers, or choose between two previously introduced centers focused on addition and subtraction within 20.

As needed, revisit and reinforce the structures and norms for centers that were established in previous lessons.

As students worked together today, where did you see evidence of the mathematical community established over the course of the school year?