What is used when a quick estimate of the doubling time is needed?

The Rule of 72 is commonly used for estimating how long it will take for an investment to double in value at a fixed annual rate of return. This rule provides a quick and simple way to calculate doubling time by dividing 72 by the expected annual rate of return expressed as a percentage. For example, if you anticipate an annual return of 6%, you would divide 72 by 6, resulting in an estimate of 12 years for the investment to double.

This rule is particularly effective because it provides a reasonably accurate estimate without the need for complex calculations. Its usability lies in its simplicity and accessibility, making it a popular tool among investors and financial planners.

The other options, while they may represent various estimation techniques, do not serve as standard methods for quickly estimating doubling time in the way that the Rule of 72 does.