Interest & Compounding

Money that grows on itself

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Simple interest pays on the original amount; compound interest pays on the growing balance.
• Compound growth: amount $= P(1 + r)^n$.
• Rule of 72: doubling time ≈ 72 ÷ rate (in %).

Steps

1. Simple versus compound
2. Watching it grow
3. Ten years at 5%
4. Double your money
5. Monthly compounding
6. Bernoulli’s question
7. Rule of 72