An explorer undertakes to cross a desert with the help of porters. The length of the trail corresponds to 6 days walk. But the explorer, like each porter, can carry only 4 days food. How many porters does the explorer need? In fact, can he cross at all?
REVEAL THE ANSWER
The explorer can cross the desert using only two porters. They all leave one morning, each with 4 days food. At the end of the first day, each has 3 days food left. The first porter goes back with one days food, leaving 4 days food each for the explorer and the second porter. At the end of the second day, the two men each have 3 days food. The second porter goes back with 2 days food. The explorer goes on with 4 days food, enough to reach his goal.
