Module 4 culminates with Topic F, in which students think about and discuss the multiple strategies they have learned to represent and solve addition and subtraction problems. They share their reasoning as they link their drawings to two written methods, and discuss the similarities, differences, and efficacy of each approach. In Lesson 29, students learn the totals below written method. Throughout Grades 1 and 2, students decompose numbers into expanded form to recognize place value and to understand that they must add like units. These problems are written horizontally. Here, students use this prior learning to solve addition problems in a similar way. They decompose two- and three-digit numbers, then add like units and record the totals horizontally (see image below). They then transition into the vertical form of the method when they decompose the numbers mentally, add like units, and record the totals below. The totals below method gives students the option of adding from left to right or from right to left. Students explain how each step of their math drawing relates to this written method. In Lesson 30, students represent and solve problems using both the totals below and the new groups below methods (students used the latter method throughout the module). They relate both methods to their math drawings and discuss the differences and similarities between the two. In Lesson 31, students apply knowledge of addition and subtraction strategies to solve two-step word problems. Students are challenged to make sense of more complex relationships as they are guided through more difficult problem types, such as comparison problems. These problems will involve smaller numbers and will be scaffolded to address the heightened level of difficulty.
Grade 2 Mathematics Module 4, Topic F
Common Core Learning Standards
|2.OA.1||Use addition and subtraction within 100 to solve one- and two-step word problems involving...|
|2.NBT.7||Add and subtract within 1000, using concrete models or drawings and strategies based on place value...|
|2.NBT.9||Explain why addition and subtraction strategies work, using place value and the properties of...|