This is the first of a series of posts about teaching decimal fractions, a topic many teachers say is one of the hardest in the curriculum.

### Rationale

There is widespread research and anecdotal evidence that shows that decimal fraction concepts are poorly understood by many students. Unlike whole numbers that can be modeled effectively using place-value blocks and other base-ten material, rational numbers present a number of difficulties for effectively modeling them. In particular, it is difficult for some students to perceive the “whole-part” notion that is at the heart of all rational number concepts. The models used by teachers must be chosen and used carefully, to avoid giving students unwanted ideas.

### Computer Technology: A Possible Solution

The computational capabilities of computers have been put to good use by software developers, in “bringing math to life” for young students. However, many programs focus on drill and practice, rather than the development of number concepts. A later post in this series describes a computer program that models decimal fractions, as an example of how computer technology can be used in mathematics teaching. The capabilities of the computer allow the models for rational numbers to be linked to written symbols for numbers, and to be manipulated in ways not possible with physical materials.

### What is the Problem?

Both research evidence and stories from teachers show that many students find decimal fraction concepts difficult to understand. In fact, decimals are members of a larger set of numbers, that we call rational numbers.