if sushi rows 27 km upstream and 81 km down steam taking 9 hours each , then the speed of the stream
speed upstream = 27 / 9 = 3 kmph speed down stream = 81 / 3 = 27 kmph speed of stream = ½ ( 27 - 3 ) = 12 kmph answer : a
add(divide(81, 9), divide(27, 9))