Lesson plan

Compare numbers within 1000 using a bar model to find the difference

teaches Common Core State Standards CCSS.Math.Content.2.NBT.B.7 http://corestandards.org/Math/Content/2/NBT/B/7
teaches Common Core State Standards CCSS.Math.Practice.MP1 http://corestandards.org/Math/Practice/MP1
teaches Common Core State Standards CCSS.Math.Practice.MP7 http://corestandards.org/Math/Practice/MP7

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Big Ideas: Addition and subtraction are related operations. Models and drawings can be used to solve addition and subtraction problems. In this lesson, students are asked to compare three digit numbers using Bar Model to find the difference. Specifically, students compare the number of miles different types of whales can swim in one day. The information about the whales is presented using a bar graph. This builds on students' previous work with graphs, but includes the totals as these are scaled graphs. This supported exposure to a scaled graph prepares students for work in third grade (3.MD.3). Comparison word problems are a challenging type for second grade students and the Bar Model (also called Part-Part-Whole Diagram or Tape Diagram) scaffolds their understanding of relative number size and missing parts. Students generally start out using a subtraction equation to solve comparison problems but may move to a missing addend equation. Bar Models also develop students' understanding of the relationship between addition and subtraction. Vocabulary: bar model, represents, miles, length, bar graph, equation Special Materials: Paper or individual white boards.