Unit 2 Contents

Number Sentences

1. Is the number sentence above true or false? Tell how you know.
2. 2 + 9 + 8 =

For each of the problems below, decide if the number sentences in A and B are true or false. Then solve C. Be ready to explain your thinking.

1. 19 + 5 =19 + 1 + 4
2. 19 + 1 + 4 = 20 + 4
3. 19 + 5 =
1. 7 + 6 + 3 = 7 + 3 + 6
2. 7 + 3 + 6 = 10 + 6
3. 7 + 6 + 3 =
1. 5 + 12 + 5 = 5 + 5 + 12
2. 10 + 12 = 21
3. 5 + 5 + 12 =
1. 8 + 9 + 3 = 8 + 2 + 7 + 3
2. 8 + 2 + 7 = 10 + 10
3. 8 + 9 + 3 =

Use the Six Key Is Broken page in the Student Activity Book to continue to look for tens in number sentences.