“Who would draw a picture to divide 2/3 by 3/4?” asked Marina Ratner, a professor emerita of mathematics at the University of California at Berkeley, in a recent Wall Street Journal opinion piece.

For many elementary teachers, fractions have traditionally sprung to mind lessons involving pizzas, pies, and chocolate bars, among other varieties of “wholes” that can be shared. But in what many ...

In this chapter, we look beyond the whole numbers at other numbers that are included in school mathematics in grades pre-K to 8, particularly in the upper grades. We first look at the rational numbers ...