Lesson objective: Estimate the sum of fractional values as greater or less than a given whole number.

This lesson provides an opportunity for students to apply their knowledge and understanding of estimation of fractional sums to a real-life situation. Students are asked to estimate a the perimeter of a polygon with fractional side lengths and decide if the result is greater or less than a given number.

Key Concept students will use:

- We can use the magnitude of fractions to be added or subtracted to estimate the sum or difference as less than or greater than some whole number, or to tell what two whole numbers the result should fall between.

Skills students will use:

- Find perimeter of polygons (Grade 3, Unit 3)
- Compare fractions to benchmark values of 0, half, and 1 (Grade 4, Unit 5)
- Use benchmark values of 0, half, and 1 to estimate sums and differences of fractional values

Students engage in Mathematical Practice 4 (Model with mathematics) as they identify important quantities in a practical situation and map their relationship using number lines or other concrete models. They model where sums and differences most reasonably fall on the number line, interpreting their mathematical results in the context of the situation and reflecting on whether the results make sense.

**Key vocabulary: **

- Perimeter
- Estimate
- Benchmark value
- Sum

**Special materials needed:**

- Students may need fraction tape to model fractional values