Pick a lesson — or pick up where you left off.
Six bite-size lessons, one per objective. Most students do them in order, but you can jump around if you want a refresher on a specific idea.
Start Lesson 01What interest actually is.
Set up interest problems by identifying principal, rate, and time, and distinguish simple interest from the total accumulated amount.
Open lessonSimple interest, the warmup formula.
Apply the simple interest formula I = Prt and the accumulated-amount formula A = P(1 + rt) to short-term lending and saving problems.
Open lessonCompound interest, and where it leads.
Apply the compound interest formula at any compounding frequency, and recognize continuous compounding as its limit.
Open lessonThe rate you really earn.
Compute the effective annual yield (APY) and use CPI data to find the real (inflation-adjusted) return on a savings account.
Open lessonLump sum vs. annuity.
Use the lump-sum and annuity future-value formulas to project savings forward across long time horizons.
Open lessonBuild a savings plan.
Plan for short-, medium-, and long-term financial goals using lump-sum and annuity formulas inside savings vehicles.
Open lesson