The speed at which a man can row a boat in still water is 6 km/hr. If he rows downstream, where the speed of current is 3 km/hr, how many seconds will he take to cover 80 meters?
Choose one:
A) 28
B) 32
C) 36
D) 40
E) 44

Rationale: "the speed of the boat downstream = 6 + 3 = 9 km / hr 9 km / hr * 5 / 18 = 2.5 m / s the time taken to cover 80 meters = 80 / 2.5 = 32 seconds . the answer is b ."
Answer: B