There are no tricks - this is a straightforward problem.
U2 have a concert that starts soon and they must all cross
a bridge to get there. All four men begin on the same side
of the bridge. You must help them across to the other side.
It is night. There is one flashlight.
A maximum of two people can cross at one time. Any party
that crosses the bridge, either 1 or 2 people, must have
the flashlight with them. The flashlight must be carried
back and forth, it cannot be thrown, etc. Each band member
walks at a different speed. A pair must walk together at
the rate of the slower man's pace:
* Bono: - 1 minute to cross
* Edge: - 2 minutes to cross
* Adam: - 5 minutes to cross
* Larry: - 10 minutes to cross
For example: if Bono and Larry walk across first, 10
minutes have elapsed by the time they get to the other side
of the bridge. If Larry then returns with the flashlight, a
total of 20 minutes have passed. What is the shortest
amount of time to get all four men across the bridge?
There is no trick to this. It is a simple movement of
resources in the appropriate order.