i understand ur point pilotmickey...i said the answers are perfect if they represent a simple equation and not involving the factor of time...which i did by mistake....which by the way doesnt solve inner's problem!Perfect only for another problem with mere units rather than hours.
your answer is perfectly descriptive of the real problem and gives the real solution.
happy?
really it was good explanation and indeed rather tough for an aptitude test.
maybe more suitable for a cambridge Thinking skill 3th paper....