Number Line

A number line provides a spatial representation of numerical ratios, facilitating the intuitive understanding of arithmetic operations and some of their fundamental properties

The numbers form ordered sets, within which precise ratios and relationships exist. For example, within the natural numbers, 4 is the next of 3 and the previous of 5; 9 is less than 27; 11 is greater than 10. These relations are fixed and immutable and can be expressed in a purely symbolic way (e.g., 9 < 27; 11 > 10).

However, our understanding of numerical proportions and properties can be improved and facilitated if the mathematical symbols that express them can be associated with a spatial representation of those connections. The number line precisely plays this role of support and facilitation to the advantage of our intuition of numerical quantities and properties.

In its simplest representation, and based on the use that has consolidated over time, a number line is a horizontal straight line ending with two arrows representing the infinite growth of numbers in both directions. Zero is marked with a tick in the center of the line; the positive integers, corresponding to the set of natural numbers, by convention follow each other to the right of zero at regular intervals…