A pilgrim needs to make a journey on foot between Casablanca and Marrakesh, to deliver movies to the new Marrakesh multiplex. It’s an arduous and dangerous trip at best, and it takes six days. The most a traveler can carry for food and water is four days’ worth. There are no hotels. Here’s the question: How many people must start out together, so that one of them can make it all the way to Marrakesh from Casablanca?
One other thing: The others who start out along with the pilgrim, they can’t die along the way.
October 19th, 2012 | Category: 
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3 people, each with 4 days worth of food and water.
person 1 travels 1 day.
person 2 travels 2 days.
pilgrim travels 6 days.
At the end of day 1, person 1 gives person 2 and the pilgrim 1 day of food and water each. At the end of day 2, person 2 gives the pilgrim 1 day of food and water. Pilgrim now has 4 days of food and water with 4 days of his journey remaining. Person 1 retained the 1 day of food and water he needed to return. Person 2 retained the 2 days of food and water he needed to return.
You are correct, Kyle. The answer is three people.
Let’s say person number one is the one we’re trying to get to Marrakesh.
Day one, three people start out together. That day, each of them eats the food that person number three is carrying. Person number one eats none of his own food. Person number two eats none of his. All three of them eat three days’ worth of person number three’s food.
They go to sleep. The next morning person number three has to turn back to Casablanca. He has one day’s worth of food and water left. And one day’s journey back. If he doesn’t leave, the buzzards get him. Day two begins, person number one and two continue their trip, and they eat person number two’s food. They eat half of it. This leaves person number two with two days worth of food and water left. Just enough to get back. He can just make it before the buzzards get him. Person number one hasn’t touched any of his food and water. How much of a trip does he have left to get to Marrakesh? Four days, and he has all of his food and water left.
You are today’s winner.