The U2 Riddle

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 in under or at 17 minutes. 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 the get to the other side of the bridge. Larry then returns with the flashlight, a total of 20 minutes have passed and you have failed the mission. There is no trick behind this. It is simple movement of resources in the appropriate order. There are two known answers to this problem. This is based on a question Microsoft used to give to all prospective employees. Note: Microsoft expects you to answer this question in under 5 minutes!

Good Luck!

Comments on this entry are closed.

• andreas June 1, 2005, 8:08 pm

***WARNING: SPOILER BELOW***
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bono and edge cross. 2
bono returns. 1
edge returns. 2
bono and edge cross. 2
total = 17

• jaced June 6, 2005, 11:46 am

You’re hired, and my guess is that you probably figured it out as fast as anyone. Note that you can swap Steps 2 and 4.

• andreas June 6, 2005, 12:24 pm

yeah, i figured bono had to go tell adam and larry what to do. they
might not listen to the edge.

• jaced June 18, 2005, 9:20 pm

I was humming “A Sort Of Homecoming” today and realized that if Larry and Adam didn’t listen to the Edge, then Bono would be stranded behind at Step 3 after the Edge told them to hand over the flashlight.

• Mike August 29, 2012, 4:42 pm

I hate Bono!

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