Here's a variation on fox, chicken and grain crossing a river.
U2 has a concert that starts in 17 minutes 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 only one torch. A maximum of two people can cross at one time. Any party who crosses, either 1 or 2 people, must have the torch with them. The torch must be walked back and forth, it cannot be thrown. Do they make the gig in time?
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 when they get to the other side of the bridge. If Larry then returns with the torch, a total of 20 minutes have passed and you have failed the mission.