Dear Alex:

I searched your site with hopes of an answer for this one but I cant seem to get it From what I know this is called the Rock and Roll Problem.

"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. It is night. There is one flashlight. A maximum of two people can cross at one time. Any party who crosses, either 1 or 2 people, must have the flashlight with them. The flashlight must be walked 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 when they get to the other side of the bridge. If Larry then returns with the flashlight, a total of 20 minutes have passed and you have failed the mission

I have been told that there are 2 answers to this, neither are a trick answer, can you help?

Tim Hunter
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Information Engineering Technology
College of Applied Sciences
University of Cincinnati

http://www.cojones.dyn.ml.org

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