Rule of 72 | Summary and Q&A

TL;DR

The rule of 72 helps estimate the time it takes for an investment to double by dividing 72 by the annual interest rate.

Key Insights

• 🥡 The rule of 72 is a useful tool for estimating the time it takes for an investment to double.
• ☠️ The rule of 72 formula is 72 divided by the annual interest rate.
• 🧑‍💻 The formula provides an approximation, and for more accurate results, the natural log formula can be used.
• 🧑‍💻 The formula for the natural log of the doubling time is the natural log of 2 divided by the natural log of 1 plus the interest rate.
• 📏 The rule of 72 is a simplification of a more complex formula for compound interest.
• ☠️ It is important to convert the interest rate into its decimal form when using the natural log formula.
• 😚 The rule of 72 provides a close approximation to the actual doubling time, but it may not be completely accurate in all cases.

Transcript

in this video we're going to talk about the rule of 72 and how to use it to find the time it takes to double your investment given an annual interest rate so let's focus on part a if the annual interest rate is 4 how long will it take to double your investment so the formula that you're going to use or that we're going to use rather is going to be ... Read More

Questions & Answers

Q: What is the rule of 72?

The rule of 72 is a formula that estimates the time it takes for an investment to double by dividing 72 by the annual interest rate.

Q: How accurate is the rule of 72?

The rule of 72 provides a close approximation to the actual time it takes for an investment to double, but it may not be completely accurate in all cases.

Q: How do you use the rule of 72 to find the time it takes to double an investment with a 4% interest rate?

To find the time, divide 72 by the interest rate, so it would be 72 divided by 4. The answer is approximately 18 years.

Q: Is the rule of 72 applicable only to investments with a specific interest rate?

No, the rule of 72 can be used for any interest rate. It is a general rule that provides a close estimate of the doubling time.

Summary & Key Takeaways

• The rule of 72 is a simple formula to estimate the time it takes for an investment to double, based on the annual interest rate.

• To use the rule of 72, divide 72 by the interest rate to get an approximate answer.

• For more accurate results, use the formula: natural log of 2 divided by the natural log of 1 plus the interest rate.