a man rows his boat 90 km downstream and 72 km upstream , taking 3 hours each time . find the speed of the stream ?
"speed downstream = d / t = 90 / 3 = 30 kmph speed upstream = d / t = 72 / ( 3 ) = 24 kmph the speed of the stream = ( 30 - 24 ) / 2 = 3 kmph answer : d"
divide(subtract(divide(90, 3), divide(72, 3)), const_2)