a man rows his boat 90 km downstream and 70 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 = 70 / ( 3 ) = 23 kmph the speed of the stream = ( 30 - 23 ) / 2 = 3.5 kmph answer : c"
divide(subtract(divide(90, 3), divide(70, 3)), const_2)