It Wasn't a Straight Line
by Anonymous · ⭐ 1 · 🍴 0
📈 1,000 at 6% a year for 30 years. Simple interest gives 2,800; compounding gives 5,743 — same money, same rate, a 2,943 gap. Move the three sliders. For the first year the two lines sit on top of each other; after that only one of them bends upward. Simple interest pays on the principal alone, while compounding also pays on what has already grown. ✌️ Second, doubling. Pick a rate and guess the year it doubles — it's a division, not a multiplication. 6% takes 12 years, 8% takes 9. Divide 72 by the rate and you land within a year of the true answer (the Rule of 72). ⏳ Third, starting late. Same amount, same rate; the only difference is when you began. Waiting ten years costs you 2,536 after thirty. Time beats principal. This app was made with code too · Remix it with your own rate and horizon.
About this app
Money Doesn't Grow in a Straight Line is an interactive learning app about compound interest and the effect of time on savings. Adjust the principal, annual return, and investment period to compare simple and compound growth, estimate doubling time with the Rule of 72, and see how starting ten years later changes the final result.
Use cases
- Learners exploring personal finance fundamentals
- Adults building intuition about compound interest
- Teachers demonstrating exponential growth and the Rule of 72
- Anyone comparing the cost of delaying an investment
Features
- Interactive sliders for principal, annual return, and years
- Visual comparison of simple-interest and compound-interest growth
- Doubling-time estimation activity based on the Rule of 72
- Comparison of starting now versus starting ten years later
- Reset and step-through navigation across three learning tabs
- Optional sound toggle