U2 has a concert that starts in just 17 minutes and all of the band members must all cross a bridge to get to the stage. 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 weakness 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 flashlight. The flashlight is always required when crossing the bridge and it 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
- Edge takes 2 minutes to cross
- Adam takes 5 minutes to cross
- Larry takes 10 minutes to cross
For example, if Bono and Larry walk across first, it takes them 10 minutes to cross. If Adam then returns with the flashlight, a total of 15 minutes will have passed. How do they all get across in 17 minutes?