Time to Double Investment Formula
A = Pe^rt
Sample Problem
If r = 5%, then to find double time, the formula looks like the following;
2P = Pe^.05t
we then divide both sides by P, so the equation is now;
2 = e^.05t
multiply both sides by ln
.05t = ln2
divide by .05
t = ln2 / .05
t = 13.86 years
therefore, it will take 13.86 years to double your investment based on an interest rate of 5%