Correct option is B
Solution:
If the sum triples, the interest earned = 2 times the principal.
Simple Interest formula pattern: Time ∝ Interest (when rate is same)
If 2P interest takes 15 years, then P interest will take:
Time = 15 × (1 / 2) = 7.5 years
So, the amount will double in 7.5 years.
Correct Answer: (B)