Lesson plan

Solve word problems to find perimeter of irregular polygons by using addition and subtraction strategies

teaches Common Core State Standards CCSS.Math.Content.3.MD.D.8 http://corestandards.org/Math/Content/3/MD/D/8
teaches Common Core State Standards CCSS.Math.Content.3.NBT.A.2 http://corestandards.org/Math/Content/3/NBT/A/2
teaches Common Core State Standards CCSS.Math.Practice.MP4 http://corestandards.org/Math/Practice/MP4
teaches Common Core State Standards CCSS.Math.Practice.MP6 http://corestandards.org/Math/Practice/MP6
teaches Common Core State Standards CCSS.Math.Practice.MP8 http://corestandards.org/Math/Practice/MP8

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Big Ideas: Addition and subtraction are related in a part to whole relationship. You can find the perimeter of a shape by adding the lengths of the sides This lesson builds on students' work with adding the sides to find the perimeter of a polygon. This task uses an irregular polygon with sides that are known and unknown. Students apply addition and subtraction strategies to compare side lengths to determine the missing side to find the perimeter of the polygon. By understanding that perimeter is additive, students will use different addition strategies and use rounding as one method to check the solution. The mathematical concepts in this lesson build towards students' future work with exhibiting rectangles with similar areas or perimeters using addition, subtraction, multiplication and division. Vocabulary: perimeter, distance, width, length, additive, rounding Special Materials: copy of blank trail slide (optional)