Students' Understanding of Decimals: An Overview

Abstract: Although students first learn about decimal notation in primary schools, it is well known that secondary students in many countries, including Australia, do not have an adequate knowledge of the concepts involved. Even some students who can calculate with decimals do not understand the comparative size of the numbers involved.

Understanding decimal notation is an important part of basic numeracy. Our society makes widespread use of metric measurement for scientific and everyday purposes. Computers and calculators use decimal digital displays so making sense of input and output of decimal numbers is essential.

In this article, we will demonstrate some of the ways in which students think about decimal notation and how this changes as students get older. Our testing at one school, which seems to us to be quite a typical Australian high school, showed that about a quarter of students still had important misconceptions in Year 10. We present a simple test that teachers can use to help them diagnose the mistakes that their students are making and we discuss some of the help that is appropriate. In this article "decimals" will refer to "decimal fractions" and "fractions" will refer to "common fractions".

Stacey, K., Steinle, V., & Moloney, K. (1998). Students' Understanding of Decimals: An Overview.