Two dice make a calendar

Kalender kat

Little riddle: if you have two dice (so each has 6 sides), with 1 digit on each side and you want to be able to form all numbers between 1 and 31 (for the days of the month), what digits would be on each dice? E.g. if dice #1 has 0-1-2-3-4-5 and the second 4-5-6-7-8-9, it won’t work, because you cannot form the number ‘22′.

Try to guess and I’ll give the answer next week. There’s a little trick involved! I first tried to figure it out without looking at the dice, and I enjoyed the mind gymnastics.

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15 Responses to “Two dice make a calendar”


  1. Gravatar Icon 1 Mich

    Got it ! But I won’t tell, otherwise I will spoil it for others :-/

  2. Gravatar Icon 2 Inferis

    Not that hard, is it?

  3. Gravatar Icon 3 Pascal

    out of my head!

  4. Gravatar Icon 4 Pascal

    (for the non-Dutch speakers… I meant: “done it without looking at dice and without writing anything down”)

  5. Gravatar Icon 5 Clopin

    Not that hard, but indeed fun to play with. Thanks ;)

  6. Gravatar Icon 6 Clopin

    Hmm, one question though: is it allowed to leave dice out from time to time? Because I could have a problem in the first 10 days ;)

  7. Gravatar Icon 7 Inferis

    @Clopin: I struggled with that too, but the riddle says “1 to 31″, so I assumed it was okay to represent the first 9 days using 1 dice.

  8. Gravatar Icon 8 Pascal

    @Clopin and @Inferis:

    No, you need to have two dice, otherwise it wouldn’t be much fun…
    So: you need to have “0″ on one or both dices.
    Oh, and may I point out that the digits are Arabic, and not represented by numbers of dots?

  9. Gravatar Icon 9 jan

    sorry 123456 and 789120

  10. Gravatar Icon 10 Pascal Van Hecke

    @Jan
    That would be the Clopin-Inferis way of doing it.
    You can’t form “07″, “08″ and “09″ with your solution.

  11. Gravatar Icon 11 Inferis

    It’s still not that hard then. :)

  12. Gravatar Icon 12 Peter

    Hint: you will need two 0s, two 1s and two 2s.

  13. Gravatar Icon 13 DaveR

    The 9 is there all along its just hidding.
    ;)

  14. Gravatar Icon 14 Stijn

    *spoiler warning*

    I think I got it right. (:

    Dice A: zero-one-two-three-seven-eight
    Dice B: zero-one-two-four-five-six

    The six can be used as a nine as well.

  15. Gravatar Icon 15 Brian

    With the 123456 and 789120 solution, the 1 in either die can be used as a “dash” so that two die could still be used to represent the first 9 days. That is: -1, -2, -3, etc.

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