The purpose of this activity is for students to learn Stage 3 of the Check It Off center. Students take turns picking two number cards that are multiples of 10 (0–90). Then they choose whether to make an addition or subtraction expression. Students check off the value of the sum or difference (0–90) and then write the addition or subtraction expression on the recording sheet. The partner who checks off the most numbers wins.

• Display a recording sheet with 90 checked off and 10 not checked off. 
• Display Cards 40 and 50.
• “Do you think we should add or subtract these numbers? Why?” (We should subtract because and we haven’t checked off 10 yet, but and 90 is already checked off.)

The purpose of this activity is for students to choose an activity to work on that focuses on addition and subtraction. Students choose from any of the previously introduced stages of the listed centers. They are encouraged to choose the center that will  be most helpful for them at this time.

• Five in a Row
• How Close?
• Number Puzzles

• “What is 1 thing you learned or got better at by working on the activity you chose?”