Lesson objective: Apply criteria for rounding to accurately estimate in context.

This lesson provides an opportunity for students to apply their knowledge and understanding of rounding to different place values to a real-life situation. Students are asked to estimate the number of people attending a party in order to purchase an appropriate amount of food.

Key Concept students will use:

- when rounding to estimate solutions, we make choices about which place to round to depending on units and quantities involved

Skills students will use:

- different ways to round
- number lines to locate numbers
- assessments of efficiency, reasonableness, and accuracy

Students engage in Mathematical Practice 2 (reason abstractly and quantitatively) as they contextualize numbers to ensure accuracy and decontextualize them to make computation simpler. They are able to explain the answer that they get when they round and how it relates to the exact answer.

**Key vocabulary: **

- accurate
- efficient
- estimate/estimation
- hundreds
- ones
- reasonable
- round
- tens

**Special materials needed:**

- graph paper for making number lines