Early Thursday Puzzle

[Rob_the_Saint]

Apologies for copying and pasting, I couldn't be bothered to type it all in...

 

Allegedly, this is one of the questions for potential Microsoft employees. I must warn you, you can really get caught up trying to solve this problem.

 

Reportedly, one guy solved it by writing a C program, although that took him 37 minutes to develop (compiled and ran on the 1st try though). Another guy solved it in three minutes. A group of 50, at Motorola, couldn't figure it out at all. See how long it takes you.

 

 

"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. 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.

 

Notes: There is no trick behind this. It is the simple movement of resources in the appropriate order. There are two known answers to this

problem. This is based on a question Microsoft gives to all prospective employees.

 

Note: Microsoft expects you to answer this question in under 5 minutes!

 

Don't take it too hard if you don't figure this out...

 

editors note: I was the only one in our office to get it, but it took me all morning!

[GHA EFM]

Bono and Edge go across, Bono returns: 3 minutes

Bono and Adam go across, Bono returns: 6 minutes.

Bono and Larry go across: 10 minutes.

 

19 minutes. Off the top of my head.

[Rob_the_Saint]

They'd be 2 minutes late for the concert then!

 

There are two methods of getting them all across in 17 minutes - answers tomorrow afternoon if nobody gets them first.

[GHA EFM]

The concert was delayed 2 minutes due to crowd trouble. The bridge was blocked by U2 walking back and forth across it.

[GHA EFM]

Just got it.

 

The torch has a high-powered beam, than extends to half the length of the bridge.

 

Bono takes the torch and stands in the middle of the bridge. With him is Edge. He points the torch at the far end of the bank, and Edge makes it. Therefore, in 2 minutes, Edge is on the other side and Bono is in the middle. Bono shines the light at the initial bank, and Adam walks across, directed by Bono. Another 5 minutes have gone. Bono shines the light at the initial bank and Larry starts to cross. When Larry meets Bono, they both continue to the other side, taking an overall total of 10 minutes.

 

They're all over in 17 minutes. Rob?

[Bald_Eagle]

Piss easy,

 

Bono and edge go-2 mins

bono back-1 min

adam and larry cross-10 mins

edge back-2 min

Bono and edge go 2 mins

 

17 minutes in my book............

[AFF]

Yes BE, if only it was this easy to become a VP at Microsoft. It should be straightforward to get to the top at Motorola, clearly.

 

The second alternative is for the second and fourth movements to be reversed with the same result.

[EFM's Librarian]

This all seems pretty dull to me <img src="/forums/images/graemlins/wink.gif" alt="" />

[Laz]

Easy, do they start with an intro tape?

 

If so, then the gig can start without the band being there.

 

In which case Bono makes each trip a total of 19 minutes.

 

17 with the other three members of the band and 2 for the return trips.

 

[Colin Zeal EFM]

U2?

 

I'd make them all walk across the bridge at the same time, and hope it collapses!! <img src="/forums/images/graemlins/grin.gif" alt="" />

 

 

[Laz]

Forget my previous suggestion, some clever clogs here has just got it...

 

Bono and Edge 2 minutes.

Bono returns 1 minute.

Adam and Larry 10 minutes.

Edge returns 2 minutes.

Bono and Edge 2 minutes.

 

We've just packed the guy of to Microsoft for the job as he's done it in about 3 minutes.

[Colin Zeal EFM]

Indeed Bald Eagle got it at 12.17 this morning, Laz.

 

 

[GHA EFM]

I think we all know who got it first, don't we?

 

<img src="/forums/images/graemlins/wink.gif" alt="" />

[AFF]

Yes GHA.

 

I passed on the opportunity to commend your invention earlier. A complex mind GHA. Well done.

[Laz]

I didn't bother reading BE's entry!