U2 has a concert that starts in just 17 minutes and all of the band members must all cross a bridge to get there. The four men begin on the same side of the bridge and you must help them to get across to the other side.
Due the age of the bridge, a maximum of two people can cross at one time. To make matters worse, it is night-time and there is only one torch. The torch is always required when crossing the bridge and the torch must be walked back and forth, it cannot be thrown, etc. Each band member walks at a different speed and a pair must walk together at the rate of the slower man:
Bono takes 1 minute to cross For example, if Bono and Larry walk across first, it takes them 10 minutes to cross. If Adam then returns with the torch, a total of 15 minutes will have passed. There is no trick behind this, it is the simple movement of resources in the appropriate order.
Edge takes 2 minutes to cross
Adam takes 5 minutes to cross
Larry takes 10 minutes to cross