A man rows his boat 84 km downstream and 48 km upstream, taking 2 hours each time. Find the speed of the stream?
Select:
A) 6 kmph
B) 5 kmph
C) 9 kmph
D) 8 kmph
E) 1 kmph

Rationale: "speed downstream = d / t = 84 / ( 2 ) = 42 kmph speed upstream = d / t = 48 / ( 2 ) = 24 kmph the speed of the stream = ( 42 - 24 ) / 2 = 9 kmph answer : c"
Answer: C