Description: In Lesson 1, students study the commutativity of familiar Module 1 facts that use units of 2, 3, 4, 5, and 10 to discover facts that they already know using units of 6, 7, 8, and 9. In Lesson 2, students apply commutativity in conjunction with the n + 1 strategy to solve unknown facts. Lesson 3 introduces using a letter to represent the unknown in various positions within multiplication and division problems.

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