How can a person with zero savings at 40 retire at 60 with ₹1.5 crore?

If a person, with zero savings at 40, invests ₹15,000 monthly SIP for 20 years at an assumed rate of return of 10%, the total amount invested will be ₹36 lakh and corpus will be ₹1.15 crore. At 12%, the corpus will be ₹1.5 crore. Reaching ₹2.9 crore through an SIP at 12% would require investing ₹29,000 a month.