The history of mathematics is full of rich examples that can help students to see the place of the discipline within our cultural heritage. Valuable as this can be, it also has the unfortunate side-effect of making students think that all the math has already been done and they do not get a sense that the subject is dynamic and growing. Furthermore, most modern mathematics is very complex and not accessible to students in secondary school. This article presents a mathematical topic which is historical in the sense that it was first presented almost fifty years ago but modern because it is still used billions of times each and every day all over the world--and one that students in upper primary and lower secondary school can appreciate quite readily. (Contains 1 table.)