The speed at which a man can row a boat in still water is 6.5 kmph. If he rows downstream, where the speed of current is 2.5 kmph, what time will he take to cover 90 metres?  Pick: A) 90 seconds B) 36 seconds C) 26 seconds D) 18 seconds E) 6.5 seconds

Rationale: "speed of the boat downstream = 6.5 + 2.5 = 9 kmph = 9 * 5 / 18 = 2.5 m / s hence time taken to cover 90 m = 90 / 2.5 = 36 seconds . answer : b"
Answer: B