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Free World
Joined: 01 Apr 2005
Location: Drake Hotel
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 Posted: Mon Oct 30, 2006 11:43 am Post subject: Puzzle: bridge and flashlight |
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There are 4 bandmates who need to cross a bridge to get to a concert.
Person A takes 1 minute to walk the length of the bridge.
Person B takes 2 minutes to walk the length of the bridge.
Person C takes 5 minutes to walk the length of the bridge.
Person D takes 10 minutes to walk the length of the bridge.
Only 2 people can cross at a time.
They need to take a flashlight with them each trip and they only have one, so someone will always need to cross back with the flashlight for the others.
What is the shortest time all 4 will be on the other side? |
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jajdude
Joined: 18 Jan 2003
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| Posted: Mon Oct 30, 2006 12:30 pm Post subject: |
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| If it's less than 19 minutes I don't know. |
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Free World
Joined: 01 Apr 2005
Location: Drake Hotel
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| Posted: Mon Oct 30, 2006 5:31 pm Post subject: |
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| yep, less than 19 |
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The Chewbacca Defense
Joined: 29 May 2004
Location: The ROK and a hard place
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| Posted: Mon Oct 30, 2006 6:31 pm Post subject: |
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| 17 minutes???? |
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Sleepy in Seoul
Joined: 15 May 2004
Location: Going in ever decreasing circles until I eventually disappear up my own fundament - in NZ
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| Posted: Mon Oct 30, 2006 6:35 pm Post subject: |
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| Is it less than 17 minutes? |
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The Chewbacca Defense
Joined: 29 May 2004
Location: The ROK and a hard place
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| Posted: Mon Oct 30, 2006 6:38 pm Post subject: |
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the way i worked it out it cant be any less than 17 minutes
Damn I wish someone would tell me if im right
this is driving me nuts!!!!!! |
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Free World
Joined: 01 Apr 2005
Location: Drake Hotel
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| Posted: Mon Oct 30, 2006 7:32 pm Post subject: |
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You're right Chewbacca! Good Job!
I couldn't get them across in less than 19. |
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The Chewbacca Defense
Joined: 29 May 2004
Location: The ROK and a hard place
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| Posted: Mon Oct 30, 2006 7:44 pm Post subject: |
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The way i figured it out was this
1) First A and B go across-------------2 minutes
2) B goes back across ----------------4 minutes
3) C and D go across-----------------14 minutes
4) A goes back -----------------------15 minutes
5) A and B go back ------------------17 minutes |
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jajdude
Joined: 18 Jan 2003
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| Posted: Mon Oct 30, 2006 8:51 pm Post subject: |
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| Well done. That was bothering me too. Looks so easy once you see it. |
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RACETRAITOR
Joined: 24 Oct 2005
Location: Seoul, South Korea
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| Posted: Mon Oct 30, 2006 10:00 pm Post subject: |
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| Wow, I never would've figured that out. That's a really good one. |
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