Two boats A and B start towards each other from two places, 108 km apart. Speed of the boats A and B in still water are 12 km/h and 15 km/h respectively. If A proceeds down and B up the stream, they will meet after:

Answer: Option B

Let the speed of the stream be x kmph and both the boats meet after t hour.
According to the question,
(12 + x) × t + (15 - x) × t = 108
Or, 12t + 15t = 108
Or, 27t = 108
∴ t = $$\frac{108}{27}$$ = 4 hours