227 
It is a rough calculation to know how long it will take to double an asset at a given annual interest rate.
Or we can find out the interest rates needed to double your assets within a given investment period.
So the rule of 72 equation is
Number of years to double assets x annual rate of interest = 72
If we like to double our assets in 30 years, we should invest at 2.4% of the annual fixed interest rate.
It is calculated as 2.4% = 72 / 30.
If we invest at 5% interest, it takes 14.4 years to double our assets.
It is calculated as 14.4 years = 72/5.
