Lesson 9

In previous lessons, students explored different methods for addition and subtraction with and without composing or decomposing a ten. Students used base-ten blocks, drawings, and equations to represent their methods.

In this lesson, students choose their preferred methods and representations to add and subtract. Throughout the lesson, students are asked to connect expressions and diagrams, choose their own methods for adding and subtracting, and make sense of others thinking (MP2, MP3, MP6). Listen for the ways students explain their methods to others and look for ways to help students provide feedback to one another when their representations or explanations are not clear.

• Create a set of cards from the blackline master for each group of 2–3.

Reflect on whose thinking was heard today. Reflect on whose thinking was not heard but could have enriched the conversations. What prompts or structures might better enable the latter to share their voices and reasoning?