Lesson 9

Workshop: Reasoning from Known Facts

Est. Class Sessions: 2

Summarizing the Lesson

Write the following addition facts on the board. Have connecting cubes available to students who may need them as a direct model.

5 + 6 8 + 7 7 + 5 9 + 4

Ask:

What facts might help you solve 5 + 6? (5 + 5 or 6 + 6)
How can you use that fact? (Possible response: I know 5 + 5 so 5 + 6 is one more or 11; I know 6 + 6 so 5 + 6 is one less.)

Ask students to choose one of the other problems on the board and name a fact that would help them solve the addition problem.

After a few minutes, ask some students to share the known fact and strategy for solving each problem on the board. See Figure 4.

Which addition facts were helpful? (doubles and ten facts)
Which addition facts do you need to work on first then? (ten facts, doubles)

Ask student to complete the Reasoning from Known Facts pages in the Student Activity Book independently. Questions 1–4 should be problems most students can solve. Questions 5–7 extend this reasoning to slightly larger numbers. This will help you differentiate students who are ready to extend and apply this reasoning. Encourage all students to try the problems. The problems are supported with ten frames and number lines so all students should be able to use a direct model to solve the problem if needed.

Use the Reasoning from Known Facts pages in the Student Activity Book to assess students' abilities to use mental math strategies and reasoning strategies (e.g., using doubles, making ten) to solve addition problems within 20 [E2].

Adventure Book: