The University of Saskatchewan's Department of Mathematics and Statistics provides high school students with an online tutorial on decimal expansions. It begins with a focus on decimal representation of real numbers, followed by how this relates to integers, rational and irrational numbers. Students can access accompanying examples within the tutorial. After you can also test your skills in a series of increasingly more difficult exercises by clicking on the three coloured dots at the bottom of the tutorial page. Each of the three problem sets include hints and solutions.