Problema Solution
It takes nine days to cross a desert. A man must deliver a message to the other side, where no food is available, and then return. One man can carry enough food to last for 12 days. Food may be buried and collected on the way back. There are two men ready to set out. How quickly can the message be delivered with neither man going short of food?
Answer provided by our tutors
The men should set out together, each carrying 12 days' worth of food.
After three days of travel, one of the men should give the other three day's worth of food, and bury another three days' worth. He will have 3 days' worth remaining, which he should use to return to the original side of the desert.
The man continuing in the desert has 12 days' worth of food remaining. He should use six days to cross to the other side and deliver the message, and then six days to return to the point where the food was buried. There will be three days' rations there: enough for him to return to the original side of the desert.
So the message can be delivered in the minimum 18 days it would take to cross the desert anyways.