The purpose of this activity is for students to build an understanding of the relationship between addition and subtraction (MP7). By using two different colored cubes, students can see the two parts that make the total. They can also see when one part is removed from the total, the other part remains. Students write addition and subtraction equations to represent each cube tower.

• Invite previously identified students to share.
• “How are the addition and subtraction equations that match this cube tower the same? How are they different?” (They have the same total and the same parts. The addition equation shows that the two parts are put together to get the total. The subtraction equation starts with the total and one part is taken away and the other part is left.)

The purpose of this activity is for students to find the number that makes an addition or subtraction equation true. The equations encourage students to use methods based on the relationship between addition and subtraction (MP7). For example, after finding the number that makes   true, students can use this understanding to find the number that makes true.

• Invite previously identified students to share.

The purpose of this activity is for students to identify the differences within 10 they do not yet know from memory. Students write these differences on index cards which can be used for students to build fluency. It is not important for students to accurately distinguish between sums they recall from memory and those they find with fluency using a strategy. The focus of the lesson should be identifying the differences that take students longer to find and to develop strategies for finding the value of these differences with increased fluency. Students will continue to practice recalling sums and differences within 10 from memory in grade 2.

• “Choose one difference you are still working on. Tell your partner the sum that can help you find the value of the difference.”