Tools & Resources
Curated extras for Topic 3: interactive tools, supplemental videos, and references. Pick what helps. Skip what doesn't.
Hands-on widgets for poking at the math. Drag a slider, watch the line move.
Compound Interest Lab
Drag the principal, rate, and time. Watch six curves, see the APY ranking, and find out how much compounding earned you over plain simple interest.
Retirement Planner
Stream of monthly deposits, decades of compounding. Watch the contribution band stay thin while the interest band balloons — then compare two start ages side by side.
Financial Formulas Calculator
Pick one of the seven ALEKS dictionary formulas, pick which variable is missing, fill in the rest. Includes a downloadable Excel workbook.
Compound interest introduction | Interest and debt | Finance & Capital Markets | Khan Academy
Sal builds A = P(1+r/n)^(nt) from scratch by compounding $100 yearly, then quarterly, then monthly, watching the year-end balance creep up each time. Useful if the formula in our lesson feels like it appeared out of nowhere — this video shows you where the pieces come from.
e and compound interest | Interest and debt | Finance & Capital Markets | Khan Academy
The classic Bernoulli thought experiment: $1 at 100% interest compounded once gives $2, twice gives $2.25, monthly gives $2.61, daily gives $2.71… and that limit is e. Watch this right after our continuous-compounding section if you want to see why e shows up in A = Pe^(rt) and isn't just a magic constant the textbook handed you.
Compound Interest Formula Explained, Investment, Monthly & Continuously, Word Problems, Algebra
Pairs both formulas — A = P(1+r/n)^(nt) and A = Pe^(rt) — and drills them on the same scenarios so you can see the continuous version as the limit of the discrete one in dollar terms. Good if you want to drill problems before a quiz rather than re-watch a derivation.
Annual Percentage Rate (APR) and effective APR | Finance & Capital Markets | Khan Academy
The 'effective APR' Sal computes here is exactly our APY formula, Y = (1+r/n)^n − 1, applied to a credit card example. Watching it from the borrowing side first actually clarifies the savings side: same math, one number is what they pay you, the other is what you pay them.
Something's Eating Your Money!
PBS-quality 6-minute explainer of why a 5% APY isn't really 5% if inflation is 3%. Hits the cost-push vs demand-pull distinction without getting jargon-heavy, and lands the purchasing-power point that motivates our real-vs-nominal section.