This is supposed to be one of the questions for potential Microsoft employees. Microsoft expects you to answer this question in under 5 minutes!
"U2" has a concert that starts in 17 minutes and the group members 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 who crosses, either one or two people, must have the flashlight to see. 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, based on this information:
*Bono - 1 minute to cross
*Edge - 2 minutes to cross
*Adam - 5 minutes to cross
*Larry - 10 minutes to cross
For example, if Larry and Bono 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 will have passed and you will have failed.
Solution:
| Send Bono over with Edge: | 2 minutes |
| Bono returns: | 1 minute |
| Adam and Larry go over: | 10 minutes |
| Edge returns: | 2 minutes |
| Bono and Edge go over: | 2 minutes |
Correctly solved by:
| 1. Michael Leatherman | Norfolk, VA |
| 2. Jia Ran | Rome, Italy |
| 3. Brian Wempe | Emmaus, PA |