a man rows his boat 80 km downstream and 45 km upstream , taking 2 1 / 2 hours each time . find the speed of the stream ?
"speed downstream = d / t = 80 / ( 2 1 / 2 ) = 32 kmph speed upstream = d / t = 45 / ( 2 1 / 2 ) = 18 kmph the speed of the stream = ( 32 - 18 ) / 2 = 7 kmph answer : d"
divide(subtract(divide(80, 2), divide(45, 2)), const_2)