The Rule of 72: How Long Until Your Money Doubles?
A one-second trick: divide 72 by the yearly interest rate to estimate how many years it takes money to double. Watch $100 grow at 8% a year until it doubles at year 9, then check 6% (about 12 years) and 3% (about 24 years).
Made with
Claude Opus 5.5Anthropic
The prompt
Made in the educationalaivideos Studio. Topic: The Rule of 72: divide 72 by a yearly interest rate to get roughly how many years it takes money to double. At 8% a year it takes about 9 years, at 6% about 12, at 3% about 24. Audience: General audience scrolling short videos; no maths background Length: 30s, vertical Notes: Open on the hook: "How long until your money doubles? There's a one-second trick." Show a bar of money growing at 8% with a year counter until it doubles at year 9, then the rule (72 ÷ rate = years to double) with two quick examples. Say in one short clause that it's an approximation that works best for rates between about 4% and 12%. Not financial advice: never recommend an investment. Checked numbers: 1.08^9 = 1.999, 1.06^12 = 2.012, 1.03^24 = 2.033. This is one of the library's launch videos, so hold it to a very high bar: smooth transitions, something meaningful moving on screen at all times, a clean uncluttered layout, and nothing cropped at the frame edges. Before finishing, snapshot the final video at least every 10 seconds and fix anything cropped, overlapping or too small to read.
Transcript
How long until your money doubles? There's a one-second trick. Say your money grows eight percent a year, and each year's growth builds on the last. Year one, year two, and by year nine, it has doubled. Here's the trick: divide seventy-two by the rate. Seventy-two divided by eight is nine. At six percent? Seventy-two over six: about twelve years. At three percent, about twenty-four. It's an approximation, best for rates between about four and twelve percent. That's the Rule of seventy-two.
In the public domain: use it for anything, no permission or credit needed.