The height of an airplane as it descends to an airport runway is a quantity which has a unit that is usually rounded to a certain terminating degree of accuracy (i.e. 1, 2, ..., n decimal places)
Thus the set of rational numbers best describes the height of an airplane as it descends to an airport runway.
A rational number is a number which can be represented in the form a/b where a and b are integers. It is usually identified by a terminating or a recurring decimal number.
