a man rows his boat 90 km downstream and 5 ` 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 = 51 / ( 3 ) = 17 kmph the speed of the stream = ( 30 - 17 ) / 2 = 7 kmph answer : a"
divide(subtract(divide(90, 3), divide(5, 3)), const_2)