a man swims downstream 40 km and upstream 56 km taking 8 hours each time , what is the speed of the man in still water ?
"40 - - - 8 ds = 5 ? - - - - 1 56 - - - - 8 us = 7 ? - - - - 1 m = ? m = ( 5 + 7 ) / 2 = 6 answer : a"
divide(add(divide(56, 8), divide(40, 8)), const_2)