High School Finance

Add up coins and bills.

Cents are decimals of a dollar — every transaction is decimal arithmetic.

Build $1.37 with the fewest coins — a classic problem.

Hourly, salaried, overtime — and how to compare offers fairly.

20% off — what does that actually cost?

What interest is, why borrowers pay it, why savers earn it.

Interest on the original amount only — clean and predictable.

Interest earns interest. Slide the years and watch the curve bend up.

Why A = P(1 + r/n)^(nt) — and where every letter comes from.

Income in, expenses out — build a balanced month.

Convert between dollars, euros, pounds and more.

What a return is, what risk is, and why time helps.

Regular payments — how to value a stream of cash flows.

What a future dollar is worth today — discount it back.

Sum of discounted cash flows — positive means it's worth doing.

The discount rate that makes NPV zero — investing's headline number.

Pool small premiums, pay big claims — risk-sharing as maths.

When does owning beat renting? A comparison you can run with numbers.

Per-cent means per-hundred. Slide it and see it.

How much bigger or smaller? And how far off your estimate was.

Three ways to write the same part of a whole — and how to switch between them.

What number times itself is 16? See roots as the inverse of powers.

6.02 × 10²³ — a tidy way to write very big or very small numbers.

What number, multiplied by itself three times, gives this?

Square, cube, fourth, fifth — the general inverse of powers.