The purpose of this activity is for students to learn Stage 3 of the What's Behind My Back? center. Students find the unknown part to make 10. Students begin with a tower of 10 cubes. One student snaps the tower into 2 parts, puts 1 part behind their back, and shows the other part to their partner. Their partner records an addition equation with a blank to represent the unknown part. They then figure out how many cubes are behind their partner’s back and complete the equation.

• Invite previously identified students to share.
• “How did you figure out how many cubes were hiding behind your partner’s back?”

The purpose of this activity is for students to choose activities focusing on adding and subtracting within 10. Students choose from three centers introduced in the previous section and one center introduced in the previous activity.

• What’s Behind My Back?
• Five in a Row: Addition and Subtraction
• Check It Off
• Find the Pair

Students may work with more than one center during this time. Keep the materials from each center organized to use in future lessons.

• “How do you know that the center you chose was a good choice?”