a man swims downstream 30 km and upstream 18 km taking 3 hours each time , what is the speed of the man in still water ?
30 - - - 3 ds = 10 ? - - - - 1 18 - - - - 3 us = 6 ? - - - - 1 m = ? m = ( 10 + 6 ) / 2 = 8 answer : b
divide(add(divide(18, 3), divide(30, 3)), const_2)