Decomposing and Composing Fractions for Addition and Subtraction
What?
4.NF.B.3. Understand a fraction a/b with a > 1 as a sum of fractions 1/b.
4.NF.B.3a Understand addition and subtraction of fractions as joining and separating parts referring to the same whole.
4.NF.B.3b Decompose a fraction into a sum of fractions with the same denominator in more than one way (3/8=1/8+1/8+1/8; 3/8=1/8+2/8; 2 1/8=1+1+1/8= 8/8+8/8+1/8), recording each decomposition by an equation. Justify decompositions by using a visual fraction model.
Generation Genius - Intro to Fractions Using a Number Line
Generation Genius- Add and Subtract Fractions with Like Denominators
Why?
In this unit students extend their prior knowledge of unit fractions with denominators of 2, 3, 4, 6, and 8 from Grade 3 to include denominators of 5, 10, 12, and 100. In Grade 4, students use their understanding of partitioning to find unit fractions to compose and decompose fractions to add fractions with like denominators. This is foundational for work with fractions later in the year, such as comparing fractions and multiplying fractions by a whole number.