• Re: 164. - THE POTATO PUZZLE

    From David Entwistle@qnivq.ragjvfgyr@ogvagrearg.pbz to rec.puzzles on Sun Aug 24 08:42:57 2025
    From Newsgroup: rec.puzzles

    On 23/08/2025 20:25, Charlie Roberts wrote:
    Is this not the Moser Circle Problem, stated in a different manner?

    I'd say a variation, but definitely related.
    --
    David Entwistle
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  • From David Entwistle@qnivq.ragjvfgyr@ogvagrearg.pbz to rec.puzzles on Sun Aug 24 08:45:39 2025
    From Newsgroup: rec.puzzles

    On 23/08/2025 09:23, Richard Heathfield wrote:
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    Well done. I derive the formula for the number of bits of potato as:
    (n^2)/2 + n/2 + 1, where n is the number of cuts.
    --
    David Entwistle
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  • From David Entwistle@qnivq.ragjvfgyr@ogvagrearg.pbz to rec.puzzles on Sun Aug 24 08:59:42 2025
    From Newsgroup: rec.puzzles

    On 23/08/2025 08:35, David Entwistle wrote:
    Take a circular slice of potato, place it on the table, and see into how large a number of pieces you can divide it with six cuts of a knife.

    Would anyone like to attempt a solution for the maximal division of a
    solid, roughly spherical, potato dissected by n planes?

    My imagination suggests:

    n = 0, 1 piece.
    n = 1, 2 pieces.
    n = 2, 4 pieces.
    n = 3, 8 pieces.

    So far so good. At this point I resorted to cutting a real potato, and
    with n = 4 got 13 pieces, but as every piece had skin on it, I suspect
    my cuts did not result in the maximal number of pieces. 16 suggests
    itself as a obvious answer, but I'd not be very confident in that assertion.

    Any takers?
    --
    David Entwistle
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  • From Richard Heathfield@rjh@cpax.org.uk to rec.puzzles on Sun Aug 24 09:24:05 2025
    From Newsgroup: rec.puzzles

    On 24/08/2025 08:59, David Entwistle wrote:
    On 23/08/2025 08:35, David Entwistle wrote:
    Take a circular slice of potato, place it on the table, and see
    into how large a number of pieces you can divide it with six
    cuts of a knife.

    Would anyone like to attempt a solution for the maximal division
    of a solid, roughly spherical, potato dissected by n planes?

    My imagination suggests:

    n = 0, 1 piece.
    n = 1, 2 pieces.
    n = 2, 4 pieces.
    n = 3, 8 pieces.

    So far so good. At this point I resorted to cutting a real
    potato, and with n = 4 got 13 pieces, but as every piece had skin
    on it, I suspect my cuts did not result in the maximal number of
    pieces. 16 suggests itself as a obvious answer, but I'd not be
    very confident in that assertion.

    Any takers?

    Martin Gardner took a crack at this in a book I (alas) no longer
    possess, entitled something like "More Mathematical Recreations
    and Diversions" and published in the 17th century IIRC.

    He used cocktail sticks to hold some of the pieces in place.

    There is, of course, an equation to give the answer to the impatient.
    --
    Richard Heathfield
    Email: rjh at cpax dot org dot uk
    "Usenet is a strange place" - dmr 29 July 1999
    Sig line 4 vacant - apply within

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  • From David Entwistle@qnivq.ragjvfgyr@ogvagrearg.pbz to rec.puzzles on Mon Aug 25 11:31:26 2025
    From Newsgroup: rec.puzzles

    On 24/08/2025 08:59, David Entwistle wrote:
    Would anyone like to attempt a solution for the maximal division of a
    solid, roughly spherical, potato dissected by n planes?

    My second attempt involved wrapping cling film around the three-cut eight-piece potato. I got a solid 14 pieces ...
    --
    David Entwistle
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  • From David Entwistle@qnivq.ragjvfgyr@ogvagrearg.pbz to rec.puzzles on Tue Aug 26 09:44:41 2025
    From Newsgroup: rec.puzzles

    On 24/08/2025 08:59, David Entwistle wrote:
    On 23/08/2025 08:35, David Entwistle wrote:
    Take a circular slice of potato, place it on the table, and see into
    how large a number of pieces you can divide it with six cuts of a knife.

    Would anyone like to attempt a solution for the maximal division of a
    solid, roughly spherical, potato dissected by n planes?

    My imagination suggests:

    n = 0, 1 piece.
    n = 1, 2 pieces.
    n = 2, 4 pieces.
    n = 3, 8 pieces.

    So far so good. At this point I resorted to cutting a real potato, and
    with n = 4 got 13 pieces, but as every piece had skin on it, I suspect
    my cuts did not result in the maximal number of pieces. 16 suggests
    itself as a obvious answer, but I'd not be very confident in that
    assertion.

    Any takers?


    SPOILER.
    POILER.
    OILER.
    ILER.
    LER.
    ER.
    R.
    .

    There's a very nice and comprehensive review of the intersection planes problem here:

    https://www.themathdoctors.org/cutting-up-space-using-n-planes/

    I see my dissection skills aren't yet up to scratch.
    --
    David Entwistle
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