# Brain Teaser (1) !!!

Discussion in 'Random Discussion' started by oldie, Oct 20, 2003.

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BRAINTEASER NUMBER 1

There are no tricks - this is a straight forward problem. This is supposed to be one of the questions which potential Microsoft employees are asked

U2 have 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 that crosses the bridge, either 1 or 2 people, must have the flashlight with them. The flashlight must be carried 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 by the time 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.

There is no trick to this. It is a simple movement of resources in the appropriate order. There are two known answers to this problem. Microsoft expects you to answer this question in under 5 minutes!

Took me a little longer Oldie

2. ### marcus77

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HA! I finally got it!!!

Bono & Edge go across first - 2min
Edge comes back - 2min
Hands light to Adam & Larry, who cross next - 10 min
They give the light to Bono, who crosses back - 1 min
Bono & Edge cross back last - 2 min
total time = 17min

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Who the hell cares about U2 anyway. Id just push them off the bridge.

4. ### pyritechipsGone but Never Forgotten

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First Name:
Jim
Grrrr!! Another friggen math quizzer!

5. ### john1

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i agree with redalert on this.

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7. ### pronute

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If they use a transportor it would take 20 ns.

8. ### p51

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What about piggy back rides? Bonon gives Larry a ride and returns. Edge gives Adam a ride, and returns, then Edge and Bono cross.

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Marcus77 - almost there but not quite - clue !!!

2 people cross
1 goes back
2 people cross
1 goes back
2 people cross

There are no tricks of people being carried on someone else's back, etc.

OK, which people cross at which time still has to be worked out. There's only 17 mins.

Larry takes 10 mins, Adam 5. You can't allow them to cross separately, since that would be 15 mins, and you'll never solve the puzzle. So they cross together. Which takes 10 mins. You can't allow either of them to make the return trip with the flashlight either, can you? Since they would still have to get back across again. That would take too long.

Regards - Oldie

10. ### angelize56Always remembered in our hearts

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Bono & Edge go across first 2 minutes
Edge comes back with torch 2 minutes
Adam & Larry go across 10 minutes
Bono comes back with torch 1 minute
Bono & Edge go across again 2 minutes

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RSM123 - hey mate why spoil a thread that others might find entertaining - there seems little or no point to it - I am sure we could all do the same with other threads - but most of us (I hope) allow the other few thousand members to take part - maybe you should delve into Edwards web site ???

http://www.edwdebono.com/cort/index.html

With respect - Oldie

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Ok on to #2!

13. ### marcus77

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~by angelize56
That's the answer I gave, just simplified.

So, if my and angelizes' answers are incorrect, what is the correct answer?

14. ### angelize56Always remembered in our hearts

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Marcus: We're wrong!!!

Did you ever get a new cat?? I've been wondering.

Take care! angel

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OK - Here is the answer

Bono and Edge cross the bridge - 2 minutes

Bono returns with the light - 1 minute

Larry and Adam cross - 10 minutes

Edge returns with the light - 2 minutes

Bono and Edge cross the bridge - 2 minutes.

Total 17 minutes!!

Thanks for the interest - regards Oldie - can someone shoot RSM123