a man rows his boat 85 km downstream and 25 km upstream , taking 2 1 / 2 hours each time . find the speed of the stream ?
"speed downstream = d / t = 85 / ( 2 1 / 2 ) = 34 kmph speed upstream = d / t = 25 / ( 2 1 / 2 ) = 10 kmph the speed of the stream = ( 34 - 10 ) / 2 = 12 kmph answer : b"
divide(subtract(divide(85, 2), divide(25, 2)), const_2)