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

If there are 4 friends and 1 flashlight and only two of them can pass at a time then 
that will mean that has to pass 2 times per person and the last time only one

for 32 will be 31*2 + 1 = 63
in a general matter will be
T = (X-1)*2 + 1 
T = 2X - 1

so for 3 friends will be (this does not take into consideration the flashlight guy)

T = 3*2 - 1 = 5 times