A man rows his boat 75 km downstream and 45 km upstream, taking 5 hours each time. Find the speed of the stream?  Select: A) 6 kmph B) 5 kmph C) 2 kmph D) 3 kmph E) 1 kmph

Rationale: "speed downstream = d / t = 75 / ( 5 ) = 15 kmph speed upstream = d / t = 45 / ( 5 ) = 9 kmph the speed of the stream = ( 15 - 9 ) / 2 = 3 kmph answer : d"
Answer: D