A sum of money invested at compound interest triples itself in 3 years. In how many years will it become 27 times itself?

Question: A sum of money invested at compound interest triples itself in 3 years. In how many years will it become 27 times itself?

Solution:
Since the sum triples in 3 years, we can write:

Thus, it will take 9 years for the amount to become 27 times itself.