Question

Four friends are out for a walk at night and come to an old bridge. it isn’t safe to cross the bridge without a flashlight, and only two people can cross at a time. they only have one flashlight. if the same person carries the flashlight the entire time, what is the minimum number of times that person will have to cross the bridge in order for the entire group to get to the other side

Answer 1

        First the person with a flashlight and one of his friends cross the bridge. After that same person with a flashlight comes back and leads another friend to the other side. Finally he comes back again and leads the last of them. 
        Number of times that he will have to cross the bridge is 5 ( five ).