A man rows his boat 90 km downstream and 40 km upstream, taking 2 1/2 hours each time. Find the speed of the stream? Answers.
A) 6
B) 7
C) 5
D) 8
E) 15
Speed downstream = d/t = 90/(2 1/2) = 36 kmph   Speed upstream = d/t = 40/(2 1/2) = 16 kmph   The speed of the stream = (36 - 16)/2   = 15 kmph   Answer: 15
<result>E</result>
A man rows his boat 90 km downstream and 40 km upstream, taking 2 1/2 hours each time. Find the speed of the stream?