Rule of 72

How do you figure out how long it will take for the Rand to halve in value at a particular inflation rate? Use the Rule of 72! This remarkable “Rule” is very accurate, but is not mathematically exact. Let’s say that you expect inflation to average 7%. You have R1m under the mattress. How long before it is only worth R500K in buying power? You divide the number 72 by the inflation rate 72/7 = 10 years. Isn’t that clever? Say you expect inflation to average 9%, then your R1m will be worth only R500K in 72/9 = 8 years…