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

Two friends should go then one friend takes the flashlight back.Next the next two friends go and throw the flashlight back to the one friend left and they walk a crossed by thierself

Answer 2

F=flashlight carrier
n=not cariying


1.
nn   →     fn

2. nnf    ←  n

3. n    →    fnn

4. fn    ←  nn

5.     →   fnnn


answer is 5 times