A sum of money triples itself in 3 years at simple interest. In how many years will it become 9 times of itself?

12 years

We have,

A sum of money triples itself in 3 years at simple interest.

We have to find,

In how many years will it become 9 times of itself.

Triple means interest is twice than principal. And nine times means interest is 8 times of principal.

So,

       Interest           Time

       Twice               3 years

  Eight times           12  years