Strategies for Adding and Subtracting Within 1,000

Description

Students practice the simplifying strategies they learned in Module 4, but with numbers up to 1,000. They will be asked to consider which strategy is most efficient for each problem they encounter. In Lesson 1, students relate 100 more, 100 less, 10 more, and 10 less to addition and subtraction. In Lesson 2, students add and subtract multiples of 100 by counting on by hundreds. In Lessons 3 and 4, students continue to add and subtract multiples of 100 with the added complexity of some tens. Lesson 3 focuses on addition, while Lesson 4 emphasizes related strategies for subtraction. In Lesson 5, students apply the use of number bonds to decompose larger numbers, just as they did with numbers within 100. In Lesson 6, the ease of subtracting a multiple of 100 is highlighted again, as students extend their work from Module 4 using compensation (i.e., the associative property) for subtraction. Topic A closes with Lesson 7, which provides students the opportunity to solidify their new skills. They confront a variety of problems, solve them, and then share their solution strategies. Through spirited discussion, students critique the work of their peers while deepening their understanding of various strategies. The strategies taught in Topic A are designed to develop students’ conceptual understanding of addition and subtraction using models, drawings, properties of operations, and strategies based on place value. At the same time, students relate these strategies to written methods such as arrow notation and number bonds. This sets the stage for flexible thinking as students move into composing and decomposing units in Topics B and C.