This workshop provides an opportunity for teachers of grades 3 through 5 to explore how mathematical models can be used to promote a deep understanding of fractions and fractional relationships. All too often, students are taught mechanical ways to make sense out of fractions, whether in the form of an addition algorithm or a procedure that produces equivalent fractions. This course offers alternative ideas for fraction instruction and is premised on the belief that students can come to understand fractions in a number of different ways. Completion of a student interview and a final project are integral parts of this course. A variety of readings, applets, and videos form the content of this course, and participants are expected to share ideas with their online colleagues in the discussion forums.