Look, you can’t complain about this after giving us so many scenarios involving N locked chests and M unlabeled keys.

https://explainxkcd.com/3015/

  • Rentlar@lemmy.ca
    link
    fedilink
    English
    arrow-up
    83
    ·
    edit-2
    1 month ago

    For the probability that at least one arrow picked is cursed: 1/2 + 1/2 × 5/9 = 14/18 = 7/9. (The probability that you picked it the first time, plus the probability that you missed it the first time but picked it the second time).

    a dice probability calculator tells me probability of 3d6 + 1d4 at least 16 is 2/9. So the DM is correct.

    • Sidenote: it doesn’t matter whether you grab the arrows one at a time or with both hands at the same time. Unless your party is trying to figure out which arms to amputate.
    • Dragon Rider (drag)@lemmy.nz
      link
      fedilink
      English
      arrow-up
      10
      ·
      1 month ago

      The math is easier if you look for the probability that the arrows are safe. If you do it that way, it’s simply 1/2*4/9, or 2/9.

      • Rentlar@lemmy.ca
        link
        fedilink
        English
        arrow-up
        3
        ·
        1 month ago

        That is true. Cueball had asked the question in the way I described, but the check was done in the inverse which is easier to do the math on.