At what rate of simple interest per year will a sum of money double itself in 25 years?

💡 Solution & Explanation

To double, the interest must equal the principal, which is 100% of it. That 100% is earned over 25 years, so the yearly rate = 100 ÷ 25 = 4%. Check with ₹100: 4% for 25 years gives ₹100 of interest, making ₹200.