Lesson objective: Understand that whole numbers can be represented as lengths from 0 on a number line diagram with equally spaced points corresponding to the numbers 0, 1, 2, etc.

Students bring prior knowledge of the structure of rulers or other tools which measure length as having equal spaces between consecutive pairs of numbers from 2.MD.A.1. This prior knowledge is extended to the use of the more abstract number line diagram as students represent whole numbers as lengths on a number line. A conceptual challenge students may encounter is that the spaces between numbers on a number line diagram do not have to be uniform.

The concept is developed through work with the comparison between a measuring tool and a number line diagram, which provides an opportunity for students to extend their prior knowledge about rulers and number lines to develop the understanding that number lines should represent values using equal spaces between numbers.

This work helps students deepen their understanding of equivalence because the numbers on a number line diagram are evenly spaced to reflect the proportionality of numbers.

Students engage in Mathematical Practice 7 (Look for and make use of structure) as they connect the structure of measuring tools, such as rulers, to the structure of a number line.

**Key vocabulary:**

- number line diagram

**Special materials needed:**

- ruler, yardstick, meter stick, or measuring tape (optional)