What Makes Interest Compound
Compound interest is interest earned on interest already earned. Ten percent on a hundred pays ten in the first year and eleven in the second, because the second year earns on a hundred and ten. Over decades that difference dominates: money invested at twenty-five and left alone will usually beat a larger sum started at forty.
The mechanism is arithmetic, but the lesson is about time, and that is what makes it hard to teach to people who have very little money and a great deal of time. It also runs in reverse, which is the half most curricula underplay: a credit card balance compounds against the holder at rates that make the same maths punishing. One thing to keep off screen is anything product-specific: named accounts, current rates, and any suggestion of what a student should actually do belong outside a classroom video.
The idea is broken into six scenes: one on simple against compound interest, two following two savers who start fifteen years apart, one on what frequency of compounding changes, one on debt compounding in the other direction, and one on the rule of seventy-two as a mental check.
