Lesson plan

Measuring benchmark angles by using fractions of a circle

teaches Common Core State Standards CCSS.Math.Content.4.MD.C.5a http://corestandards.org/Math/Content/4/MD/C/5/a
teaches Common Core State Standards CCSS.Math.Content.4.MD.C.5b http://corestandards.org/Math/Content/4/MD/C/5/b
teaches Common Core State Standards CCSS.Math.Practice.MP4 http://corestandards.org/Math/Practice/MP4

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Big Ideas: Benchmark angles are angles that are easy to work with. Common benchmark angles are formed by 1/12, 1/8, 1/4, 1/2 and 3/4 turns in a circle. Every circle has four 90-degree angles. This lesson continues to lay the foundation for angle measurement by introducing benchmark angles and making the connection between fractional turns of a circle and degree measurement. The concept that circles can be divided into equal portions is explored as students discover benchmark angles that are easily divided. They soon discover that by dividing the number of turns by 360, angle measurement can be determined. This prepares students for the use of a protractor and precise angle measurement. Vocabulary: benchmark angle Special Materials: circle template