a man swims downstream 40 km and upstream 30 km taking 5 hours each time , what is the speed of the man in still water ?
"40 - - - 5 ds = 8 ? - - - - 1 30 - - - - 5 us = 6 ? - - - - 1 m = ? m = ( 8 + 6 ) / 2 = 7 answer : e"
divide(add(divide(30, 5), divide(40, 5)), const_2)