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Another Boat Question. Need help though!

  1. Oct 5, 2006 #1
    There is only one boat. The boat can support a tiger and it's owner, or 2 owners. There are 3 tigers and 3 owners. When a owner leaves a tiger alone, the tiger will eat everything around it (tigers or humans). One of the tigers can row the boat.

    How do you get all the tigers and thier owner to the other side of the lake?
  2. jcsd
  3. Oct 6, 2006 #2
    Here's a solution, but I don't know if it is optimal. No tiger rows in this solution. Tigers are ABC, owners are abc.

    1. ABCabc -
    2. ABab - Cc
    3. ABabc - C
    4. ABa - Cbc
    5. ABab - Cc
    6. Aa - BCbc
    7. Aab - BCc
    8. b - ABCac
    9. bc - ABCa
    10. -ABCabc

  4. Oct 6, 2006 #3
    If I understand correctly, the tigers cannot be apart from their particular owners, or else the tiger eats *everything* that's on its present side?

    And, if that's the case, I'm not sure I see a solution, unless there's some trick to the wording.

    Step 1 MUST be for either
    I) tiger to go by itself
    II) tiger goes with its owner (arbitrarily (A) and (a))

    I) is obviously useless, since the only possible following step would take you back to where you were. Hence, II) is the only useful move.

    Step 2 MUST be: (a) goes back, leaving (A) by itself (but with nothing to eat).

    Step 3 MUST be useless, (a) goes back to the shore where he left his (A).

    If *anyone* else goes back to that shore without (a), they're eaten by (A).
    If (a) goes back to the opposite shore, he may bring a companion, but by bringing 1 and only 1 companion, he will necessarily seperate whoever his companion is from their tiger, resulting in a tiger eating everyone.

    So, I think it's impossible as stated.

  5. Oct 6, 2006 #4
    Yeaa, seem impossible too. I shall ask my friend about it.
  6. Oct 8, 2006 #5
    Yeah, definitely impossible. In order to be possible, it must pass through some state where there are 3 tigers/owners on each side, and there is not a single state where this is legal. Below are all possible combinations, and highlighted in orange are the tigers who will eat everything on their side:

    AaB | bCc
    Aab | BCc
    AaC | Bbc
    Aac | BbC
    ABb | aCc
    ABC | abc
    ABc | abC
    AbC | aBc
    Abc | aBC
    ACc | aBb

  7. Oct 9, 2006 #6
    Are you reading this as "When an owner leaves their own tiger alone"?
  8. Oct 9, 2006 #7
    It's an unclear question-- there are LOTS of holes. But I was reading it as:

    "when an owner is separated from their tiger, the tiger will destroy any other owners or tigers that are with them."

    If read as "when a tiger is left alone", then the "eat everything around it (tigers or humans)" becomes meaningless. Further, if read as "when a tiger is left without any owners around", then the "humans" becomes meaningless.

    For the record, I'm interpreting the problem as:


    There are 3 tigers, each with its own owner. The 3 tigers and 3 owners must cross a lake using only a particular boat. All of the tigers and owners are presently on the same side of the lake. The boat they must use is capable of carrying a maximum of 2 occupants. To be used, the boat must have at least one human present, or a single particular tiger whose identity is unknown. The two remaining tigers cannot use the boat individually or together. If a tiger is seperated from its owner at any time, the tiger will consume all owners and tigers that are with it, meaning on its side of the lake or within the boat itself during the journey.

    How are all 6 individuals able to cross the river such that they will all be on the opposite side at the same time, without any tigers or owners being consumed?


    As with so many teasers that are posted here, this one is poorly worded.

    - In the wording, it states "the boat can support a tiger and its owner, or 2 owners". So, according to the problem, single individuals cannot use the boat, the boat MUST be used by two individuals, and one of them MUST be a human. You could assume that a single person and/or tiger could use the boat, but if you do so, there's no reason to assume that all 6 couldn't use the boat at the same time.

    - It says "when an owner leaves a tiger alone, the tiger will eat everything around it (tigers or humans)." Technically, this means that the tiger will NEVER eat anything around it, because if it's ever alone, there will be nothing to eat. Hence, any combination is fine.

    - It never states that they must use the boat to cross. They could just walk around the lake. Or swim across. Or whatever.

    Anyway, there are seemingly plenty of reasons why the given problem isn't possible, or why it IS possible using an unintentional interpretation.

  9. Oct 9, 2006 #8

    True, though it would be OK for the tiger to row.
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