People who belong to the equity market or any financial market know about the Rule of 72 very well. This is one of the basic principles that everybody uses. This one is nothing more than a simple illustration of how quickly money will double at a given interest rate. It works by dividing 72 by our annual compound interest rate and seeing how many years it will take for our investment to double. But this one is only applicable to compound interest rates or any compounding calculation. Any index that compounds, like inflation, population, credit card interest, loan interest, and so on, can be used with this formula. Basically, the formula is; Number of years to double = 72/ annual interest rate For instance, if I consider someone who can earn an annual interest rate of 8%, their money will double in 72 x 8% = 9 years. Similarly, we can also use this one in the case of GDP growth. If Indian...