According to 8-4-3 rule of compounding, a person investing ₹20,000/month in an instrument that gives 12% interest per annum would make ₹32 lakh in eight years assuming it is compounded annually. Another ₹32 lakh is made in four years at same interest rate. The amount left for another three years along with ₹20,000/month investing, the corpus would become ₹1 crore.