a man swims downstream 72 km and upstream 45 km taking 9 hours each time ; what is the speed of the current ?
"explanation : 72 - - - 9 ds = 8 ? - - - - 1 45 - - - - 9 us = 5 ? - - - - 1 s = ? s = ( 8 - 5 ) / 2 = 1.5 answer : option b"
divide(add(divide(45, 9), divide(72, 9)), const_2)