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Get them across the river

  1. Jul 27, 2005 #1
    There are six people. They are: A king, A queen, A knight and his wife, A servent and his wife. There is one boat and they all want to cross the river. The problem is: the boat cannot take more than 2 people. Your job is to tell them a way so that they can all get across the river.
    Rules:
    1-Women are free to take other women with them on the boat.
    2-Men cannot take any woman except their wives on the boat.
    3-If a man finds two women alone he'll run away with them. For example, if the king finds his wife and some other woman alone. He'll run away with them. You must not allow such thing to happen.
    I hope you understand the rules.
     
  2. jcsd
  3. Jul 27, 2005 #2
    might be wronge here but...

    king picks up the queen and drops her off at the other side
    king returns for the Knight who then drops off the king at the other side
    Knight picks up his wife who then drops the knight off at the other side
    Knight's wife returns for the servants wife (but remains in the boat so the servant can't run away with the girls)
    servants wife drops off knights wife before finally picking up her husband
     
  4. Jul 27, 2005 #3
    Since the servant has two girls, he'll run away with them. So thats a wrong answer.
     
  5. Jul 27, 2005 #4
    lemme try again :biggrin:

    king drops off the queen and returns for knight
    knight drops off king and returns for his wife
    knight exchanges his wife for the king
    king and knight both disembark, servant drops off his wife
    now that all the three girls are together they can all get across
     
  6. Jul 27, 2005 #5
    The servant has now 3 girls :devil:. So he'll definately run away with them.:biggrin:
    This brain teaser does have an answer. But I wont reveal it just yet.
     
    Last edited: Jul 27, 2005
  7. Jul 27, 2005 #6

    NateTG

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    Let's call the couples AaBb and Cc.

    So we have
    AaBCc |
    King takes queen across, and returns with the boat.
    ABbCc|a
    Two wives take boat across, and queen comes back.
    AaBC|bc
    Husbands take boat across, and the knight returns with his wife.
    AaBb|Cc
    King and knight take boat across (leaving the queen and the knights wife), and
    the servant's wife takes boat back.
    abc|ABC
    The queen drops off the knights wife, on the other side, and returns
    ac|ABbC
    then the last two women cross.
     
  8. Jul 29, 2005 #7
    I'm assuming the boat can't cross the river by itself... so, does this work?

    1 - Have the SW and Q cross together.
    Over = SW & Q
    2 - Have the SW cross back over.
    Over = Q
    3 - Have the Kn and K cross together.
    Over = K, Q & Kn
    4 - Have the Kn cross back over.
    Over = K & Q
    5 - Have the Kn and KW cross together.
    Over = K, Q, Kn & KW
    6 - Have the KW cross back over.
    Over = K, Q & Kn
    7 - Have the S and SW cross together.
    Over = K, Q, Kn, S, SW
    8 - Have the SW cross back over.
    Over = K, Q, Kn & S
    9 - Have the KW and SW cross together.
    Over = K, Q, Kn, KW, S & SW
     
  9. Jul 29, 2005 #8
    Actually mine has a flaw if you mean that two women can't be alone with a man on EITHER side.
     
  10. Jul 29, 2005 #9
    I think I got it:

    Let's call them AaBbCc

    Aa -> \ BbCc | Aa - Aa(King and queen) goes over first
    A <- \ ABbCc | a - A then goes back
    bc -> \ ABC | abc - bc goes over to join a
    a <- \ AaBC | bc - a goes back
    AB -> \ aC | ABbc - AB takes the boat over
    Bb <- \ aBbC | Ac - Can't let C alone with c&b
    CB -> \ ab | ABCc - CB takes the boat
    c <- \ abc | ABC - We need our wives so c goes back to fetch them
    ab -> \ c | AaBbC - let's leave c for now
    a <- \ ac | ABbC - but then again, we're not mean
    ac -> \ | AaBbCc - We're done! Hurray

     
  11. Aug 20, 2005 #10
    knight's wife will take the knigh to the other side. then she will take the queen to the other side and then queen will return. then hmmmmmmmm then the servant and his wife will go to other bank. servant's wife will return take the queen to the other side after that queen will return again and have to take the king.
     
  12. Aug 22, 2005 #11
    The king and queen cross over first. Then the queen goes back to pick up the knights' wife and drops herself, the queen, off with her king. The knights' wife then goes back and picks up the knight, the knight gets dropped off with the king and queen. Then the knights' wife goes and picks up the servents' wife. The knights wife is dropped off w/ the king, queen, and the knight. Finally the servents' wife goes back and picks up the servent and and everyone has crossed over. And they live happily ever after....
     
    Last edited: Aug 22, 2005
  13. Jun 4, 2010 #12
    @@einsteinian77: "Then the knights' wife goes and picks up the servents' wife. The knights wife is dropped off w/ the king, queen, and the knight."
    When the knights wife returns to pickup servants wife again the equation is one men and 2 wifes so the answer is wrong
     
  14. Jun 4, 2010 #13

    BobG

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    @@einsteinian77 probably won't ever read your post, since he hasn't visited the forum in nearly 5 years.
     
  15. Jun 4, 2010 #14
    Easy queen takes one of the other women then comes back for the last one then queen comes back takes king with her then after having the 3 women on one side the king starts to bring the men over. The trick is that the men wont run away with 3 women on a side only 2. I think.
     
  16. Jun 7, 2010 #15
    @magpies If your answer was in continuation to what einsteinian77 has written then it would not work in the very first permutation where he mentions that: "The king and queen cross over first. Then the queen goes back to pick up the knights' wife and drops herself, the queen, off with her king." because when the Queen brings back the Knights wife then the king would run away with the queen and Knights wife.

    Here goes the Solution for it:

    The King and the Knight cross over first, then one of them returns lets say the king to bring the servant. The servant comes back to pick his wife and then both of them get dropped now the servants wife comes to pick the queen and both of them get dropped off at the shore now u have the option of either sending the Knight or any of those 2 womens to bring the Knights wife.
     
  17. Jun 7, 2010 #16
    @@DeathKnight Can u validate my answer
     
  18. Jun 7, 2010 #17
    That won't work. That leaves the Servant on a side all by himself with the 3 women, which he'll run off with.

    I solved it, but it took 11 crossings.

    DaveE
     
  19. Jun 14, 2010 #18
  20. Jun 17, 2010 #19
    1. King and Queen cross to side 2
    2. King comes back to side 1, Queen left at side 2
    3. Knight's Wife and Servant's Wife go to and stay at side 2, Queen comes back to side 1
    4. Servant and Knight go to side 2, Servant and Servant's Wife comes back to side 1, leaving Knight and his wife at side 2
    5. King and Servant go to side 2, Knight's Wife comes back, leaving all the men on side 2
    6. Knight's Wife and Queen go to side 2, Queen comes back
    7. Queen and Servant's Wife go to side 2, FINISHED
     
  21. Jun 22, 2010 #20
    It has been mentioned in the question clearly that if there are 2 womens with one men then they would run away he has no where mentioned that if there are more than 2 i., 3 they will run away together. I have given the explanation considering that.anyways @@shadowspirit has solved it considering this scenario as well.
     
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