The speed of a boat in still water is 15 km/hr and the rate of the current is 3 km/hr. The distance travelled downstream in 12 minutes is	Choose the correct answer.
A) 1.2 km B) 1.8 km C) 2.4 km D) 3.6 km E) none

Rationale: "speed downstream = ( 15 + 3 ) km / hr = 18 km / hr . distance travelled = ( 18 x 12 / 60 ) hours = 3.6 km . answer d"
Answer: D