Lesson objective: Determine which possible numbers will round to a given value.

This lesson helps to build procedural skill with rounding. A number line is used here because it supports the concept that numbers that are close to benchmark numbers can round to those benchmark numbers. This work develops students' understanding that rounding is based on place value and can be used to substitute close benchmark numbers.

Students engage in Mathematical Practice 8 (Look for and express regularity in repeated reasoning) as they are repeatedly exposed to rounding numbers conceptually using number lines and/or hundred charts. Students will notice the conventions of when numbers round forward or back determined by their location and distance from each other.

**Key vocabulary:**

- benchmark number
- rounding