A man rows his boat 78 km downstream and 50 km upstream, taking 2 hours each time. Find the speed of the stream?
Options:
A) 76 kmph
B) 6 kmph
C) 14 kmph
D) 7 kmph
E) 4 kmph

Rationale: "speed downstream = d / t = 78 / ( 2 ) = 39 kmph speed upstream = d / t = 50 / ( 2 ) = 25 kmph the speed of the stream = ( 39 - 25 ) / 2 = 7 kmph answer : d"
Answer: D