Lesson objective: Measure lengths on number lines and rulers with precision by partitioning into smaller pieces.

This lesson helps to build procedural skill with measuring to the nearest half, fourth and eigth. The re-partitioning of intervals on a ruler is used here because it supports students' understanding of partitioning number lines. This work develops students' understanding that measurements get more precise when we use parts of units. Length measurements can be partitioned into any size increments.

Students engage in Mathematical Practice 6 (attend to precision) as they partition number lines into smaller pieces in order to find more precise measurements of objects.

**Key vocabulary:**

- exact
- invariant
- length
- number line
- partition
- precise
- ruler