Rule of 72

I always manage to amaze my friends and clients with my speed of calculating how fast their money takes to double with the interest rate they give me.

I had actually used a very simple formula called "The Rule of 72"

The Rule of 72 formula is as follows:

Years To Double Your Money = 72 / Interest Rate

Eg, 6% interest

Years to Double your money = 72 / 6 = 12

Haha. Simple Right???