You and three of your friends have just stolen all of the pies from the Pi Day celebration.
Your group did not plan well, and your escape route takes you through a rickety footbridge. It is dark, and you have only one flashlight. A maximum of two people can cross the bridge at one time (otherwise the bridge will collapse, and you will lose all the pies). Any party that crosses, either one or two people, must have the flashlight with them. The flashlight must be walked back and forth; it cannot be thrown, for example. Person 1 takes 1 minute to cross the bridge, person 2 takes 2 minutes, person 3 takes 5 minutes, and person 4 takes 10 minutes. A pair must walk together at the rate of the slower person’s pace. For example, if person 1 and person 4 walk together, it will take them 10 minutes to get to the other side. If person 4 returns the flashlight, a total of 20 minutes has passed.
What is the minimum amount of time for everyone to cross the bridge?You are welcome to use wahtever method you wish to solve the problem.
Please submit the correct answer by April 22nd, 2016. One $10 gift card will be awarded randomly from those who submit the correct answer.
Thank you to everyone who submitted an answer (a lot of correct answers were submitted!) but sadly, there can only be one winner. The winner is: Ravi Kiran Puttaswamy.