How does inflation and the CPI relate to the Rule of 72?

Rule of 72 is a simple rule to calculate how much time it takes to double the value.

To get the answer, simply by divide 72 by the rate of change.

So for inflation rate, if it's 1% annually. then 72/1=72 years. It takes 72 years for the price to double. If it's 2% annually, then 72/2=36 years. It takes 36 years for the price to double.

The same calculation applies to CPI.