What is the shortest time to get everyone across the bridge?

1. 60

   Rubesposted 14 years ago

   What is the shortest time to get everyone across the bridge?
   
   Four people are trying to cross a bridge.   It takes each person a different amount of time to cross the bridge - it takes the first person one minute, the second two minutes, the third five minutes and the fourth ten minutes. They must cross the bridge in pairs, traveling at the slower speed so if the one minute person went with the ten minute person, it would take a total of ten minutes. Since there is only one flashlight one person must come back across the bridge, then another pair can cross. What is the shortest time to get everyone across the bridge?

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2. 59

   DonnyBoyposted 14 years ago

   What answer?
   
   ?
   ?
   ?

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   1. 58

      Sudharshan Kumarposted 11 years agoin reply to this

      17

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3. 60

   Rubesposted 14 years ago

   Sorry that is not the answer.  There is enough data to answer the question.

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   1. 58

      Sudharshan Kumarposted 11 years agoin reply to this

      No, there is enough data to ans the question... the ans is 17...

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4. 68

   hublimposted 14 years ago

   19 minutes
   1st and 2nd guy
   1st comes back
   1st and 4th
   1st comes back
   1st and 3rd
   
   hopefully the torch batteries don't run out, even better if it's a wind up torch.

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5. 72

   Quilligrapherposted 14 years ago

   Good question. 19 minutes would be my answer.
   
   Q.

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6. 0

   pauls_boatposted 14 years ago

   it cannot be done as you said there must be two peopl going across at the same time so if two go across then one cannot come back with the torch for the other peopl to cross but if they all cross at the same time in two pairs then it would take 10 minits which is the time for the slowest one to cross

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7. 59

   gamerjonposted 14 years ago

   The answer is definitely 19.
   Across:Back
          2 : 1
          5 : 1
          10
   
   2 + 1 + 5 + 1 + 10 = 19
   
   Cheers.

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8. 49

   wlyshenposted 14 years ago

   The strategy is that the slowest 2 person must cross together, and they should not return.
   
   Assume that "1" means person who takes one minute to cross, "5" means person who takes five minute, etc..
   
   Follow these sequences:
   
   - 1 and 2 cross (2 mins)
   
   - 1 return (1 min)
   
   - 5 and 10 cross (10 mins)
   
   - 2 return (2 mins)
   
   - 1 and 2 cross (2 mins)
   
   
   Total = 2+1+10+2+2 = 17 minutes

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9. 60

   Shahid Bukhariposted 13 years ago

   What Bridge ...
   
   Is it a River or an Abyss, they have to cross ...
   
   Purpose makes Time and Distances disappear.
   
   Purpose, Transcends all hurdles ...
   
   And Realizing the Purpose of Being ... makes Acting possible with Good Intent ... Faithfully ...
   
   Faith, is the Light of Life ...
   
   Humanity, has to make all crossings over, together ... as one ... and it is rather enjoyable.
   
   This is the Applied Mathematics of Belief.
   
   This is the Truth of Life.

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