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Thread: A prime number puzzle to get you thinking

  1. #1
    Join Date
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    Smile A prime number puzzle to get you thinking

    Greetings from Adelaide,


    To solve this puzzle you must fill in the grid below using the digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. Each digit must appear once in the grid.



    The 4-digit number B must be a multiple of the 4-digit number A.

    Four of the five 2-digit vertical numbers must be prime.

    No 2-digit or 4-digit number may start with a 0.

    Good luck!

    clop














    Tumkin Technology

  2. #2
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    Too difficult for you all eh?

    clop

  3. #3
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    I started giving it some thought but got distracted. I think it wouldn't be *that* difficult. I was looking at it and figured that the last digit of A must be 5 and the last digit of B must be 0. This means that the non-prime two-digit number of in the right-most slot. It also limits the penultimate number in B to either 3 or 9. Also, the numbers on the bottom row would all have to be odd, meaning that most of the numbers on the top have to be even. This gave me a pretty limited list of primes to be working from, and only a few ways to collect them to meet the use-every-digit constraint.


    That's as far as I got before a baseball game got really interesting and then I lost the puzzle on my task list.
    Forming opinions as we speak

  4. #4
    Join Date
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    30,232
    Additionally:

    Besides 0, the other digits in the bottom row are 1,3,7, and 9. (There are no two-digit primes ending in 5.)

    The first digit of A must be a 2 or a 4. (If it were any larger, then any multiple would be more than four digits.)

    The first digit of B has to be a 9. (1, 3, or 7 wouldn't work.)

    I took a couple of educated guesses after this and quickly got the answer.
    Everything I need to know I learned through Googling.

  5. #5
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    Unless I've done something appallingly silly, the solution is unique.

  6. #6
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    I only came up with one possible answer.
    Everything I need to know I learned through Googling.

  7. #7
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    Quote Originally Posted by montebianco
    Unless I've done something appallingly silly, the solution is unique.
    It is a unique solution. Rather neat really.

    clop

  8. #8
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    Oct 2001
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    It was pretty cool.
    Everything I need to know I learned through Googling.

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