Lesson objective: Understand that we can use the magnitude of fractions to be added or subtracted to estimate between which two whole numbers the result will fall.

Students bring prior knowledge of estimation with benchmarks of 0, \(\frac12\), and 1 from 4.NF.A.2. This prior knowledge is extended to include sums and differences of fractions with different denominators as students estimate sums of fractions greater than one. A conceptual challenge students may encounter is estimation of mixed numbers.

The concept is developed through work with number line and fraction tape, which aid in the development of number sense around relative magnitude of fractional values.

This work helps students deepen their understanding of number because students are estimating and reasoning quantitatively.

Students engage in Mathematical Practice 2 (Reason abstractly and quantitatively) as they attend to the meaning of quantities, not just how to compute them. They apply their knowledge of benchmark values (0, \(\frac12\), and 1) from fourth grade to estimate the relative sizes of fractional sums and differences. This reinforces the habit of making sense of quantities and their relationships in problem situations.

**Key vocabulary:**

- estimate
- benchmark value
- number line
- greater than
- less than
- between

**Special materials needed:**

- Students may need fraction tape to compare values to \(\frac12\)