A man rows his boat 72 km downstream and 30 km upstream, taking 3 hours each time. Find the speed of the stream?
Choose the correct choice from the following options:
A) 6 kmph	B) 5 kmph	C) 2 kmph	D) 8 kmph	E) 7 kmph

Rationale: "speed downstream = d / t = 72 / ( 3 ) = 24 kmph speed upstream = d / t = 30 / ( 3 ) = 10 kmph the speed of the stream = ( 24 - 10 ) / 2 = 7 kmph answer : e"
Answer: E