Lesson plan

Estimate the sums or differences of mixed numbers by comparing to a benchmark fraction (1/2)

teaches Common Core State Standards CCSS.Math.Content.4.NF.B.3c http://corestandards.org/Math/Content/4/NF/B/3/c

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Big Ideas: A numerical benchmark refers to a number to which other numbers can be related. Estimating numbers can be used to determine what a reasonable outcome will be. This lesson focuses on the process of rounding mixed numbers to estimate sums and differences. Students use their understanding of fractions on a number line and 1/2 benchmarks to determine what a reasonable outcome will be. This task uses the length of a skateboarding jump contest to highlight this reasoning skill. By leaving this task open ended, students reason why the estimate of different mixed numbers may give the same sum. The mathematics in this lesson build toward students' future work adding and subtracting mixed numbers. Vocabulary: fraction mixed number benchmark rounding estimate Special Materials: 1/4 inch rulers (optional)