Decimal Numbers on a Number Line . Number lines are a valuable representation of the rank, order, and density of numbers. Rank relates to the proportion of numbers on the number line and the spacing between them. Order relates to which numbers are larger or smaller than others and numbers positioned between other numbers. Density is the amount of numbers between numbers in a counting system. . The LTD Number Line Kits are going to make setting up and using number lines a whole lot easier for you