The amount of interest on a savings account is calculated by using the amount of money in the account and the annual percentage yield. Find out what an APY is at a bank with lessons from a math teacher in this free video on math calculations for daily life. Expert: Jimmy Chang Bio: Jimmy Chang has been a math teacher at St. Pete College for nearly a decade. He has a master's degree in math, and his specialties include calculus, algebra, liberal arts, math and trigonometry. Filmmaker: Christopher Rokosz