If a principal amount triples in 3 years under compound interest, after how many years will it become nine times the original amount?

Explanation

Since the amount triples in 3 years, it means (1 + r)^3 = 3. To get nine times the original amount, (1 + r)^t = 9. Since 9 = 3^2, t = 2 × 3 = 6 years.