This lesson introduces students to compound interest and situates it within the framework of the financial life cycle. This allows students understand why we borrow money for certain financial goals, such as college education, and invest it for others, such as retirement. Students can apply exponents in rich modelling activities, rather simply plugging in numbers into the compounding formula. The materials include a detailed lesson plan and slides, a complete set of worksheet and answer keys, along with a project-based final assessment which combines mathematical skill with financial reasoning. This provides a fresh approach to teaching both compound interest and exponents, one that allows students to critically analyze decisions regarding borrowing and investment and find an authentic application of mathematics.