Start by telling us why you're calling. 1  Here are some very popular reasons why other people call this Garmin number. 2  We have a few other tricks to try if you're calling Garmin, and if you are already viewing this on a phone or call-capable device, then you can click or tap below to just start a call.
Suppose you invest $100 at a compound interest rate of 10%. The rule of 72 tells you that your money will double every seven years, approximately: If you graph these points, you start to see the familiar compound interest curve:
The Rule of 72 helps you measure how long it will take you to double your money. BartSadowski/E+/GettyImages. The Rule of 72 is a math rule, or formula, that can give you an approximate estimate of how long it might take to double your nest egg for any given rate of return.he Rule of 72 is a math rule, or formula, that can give you an approximate estimate of how long it might take to double your nest egg for any given rate of return.