In Topic D, students relate addition and subtraction to length. They apply their conceptual understanding to choose appropriate tools and strategies (e.g., the ruler as a number line, benchmarks for estimation, tape diagrams for comparison) to solve word problems (2.MD.5, 2.MD.6). In Topic A, students had their first experience creating and using a ruler as a number line. Now, students solve addition and subtraction word problems using the ruler as a number line. This concept is reinforced and practiced throughout the module in the fluency activities that involve using the meter strip for counting on and counting back, and is incorporated into the accompanying Problem Sets. Students then progress in the second lesson from concrete to abstract by creating tape diagrams to represent and compare lengths. The third lesson culminates with students solving two-step word problems involving measurement using like units.
Grade 2 Mathematics Module 2, Topic D
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