A film on using a formula to calculate how long it will take for a student's money to grow so that she can afford to take a round-the-world trip. (Duration 4 minutes 25 seconds). Part of a series of films from the METAL (Mathematics for Economics: enhancing Teaching and Learning) project that demonstrate how the mathematics of finance can provide an insight into a range of personal and business finance issues. They are fundamental building blocks for a course of mathematics for economics. These video clips and animations can be viewed in isolation, or via the learning pathway links to related materials in a Question Bank.