The Rule of 72 states that in order to find the number of years required to double your money at a given interest rate, you divide the compound return into 72. The result is the approximate number of years that it will take for your investment to double.
For example, if you want to know how long it will take to double your money at 12% interest, divide 12 into 72 and you get six years or if at 4%, divide into 72 and you get 18 years
However it can also work in reverse if the inflation rate is say 6%, it will take 12 years for your money to fall by half in terms of purchasing power
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