a man swims downstream 48 km and upstream 18 km taking 3 hours each time , what is the speed of the man in still water ?
"48 - - - 3 ds = 16 ? - - - - 1 18 - - - - 3 us = 6 ? - - - - 1 m = ? m = ( 16 + 6 ) / 2 = 11 answer : d"
divide(add(divide(18, 3), divide(48, 3)), const_2)