The purpose of this activity is to give students practice adding and subtracting within 100. Students work in groups of 3. One student adds to find the sum of 2 numbers. The other students add or subtract to find the unknown addend when one addend and the value of the sum are known. Although the majority of sums will fall within 100, some students may create sums greater than 100.

• “What was the same about each role in this game? What was different?” (You had to figure out an unknown number in each role. Players A or B were finding an unknown addend. You can add or subtract to figure out your number. Player C always had to add.)
• “Which role did you like best—Player C or Player A or B? Explain.” (I liked to be Player C because I like to add. I liked being Player A or B because I could add or subtract. I liked being Player A or B because I could practice subtracting.)

The purpose of this activity is for students to choose the center that will most help them build their fluency for addition and subtraction within 100. These two centers were introduced in previous units and focus on adding and subtracting within 100:

• Five in a Row
• Target Numbers

• “What did you like about the activities you worked on today?”