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  • Throwing a Hundred Sided Dice

     Vivek updated 3 days, 2 hours ago 3 Members · 8 Posts
  • Puzzle Prime

    Administrator
    October 16, 2018 at 11:35 pm

    Two people are taking turns throwing a hundred sided die. The game continues until someone throws a number larger than the number thrown by the opponent on the previous turn. What is the probability that the person who throws first wins the game?

    Example: 4 – 3 – 3 – 2 – 5 => First player wins
    Example: 6 – 3 – 2 – 1 – 1 – 4 => Second player wins

  • Josefina

    Member
    November 5, 2018 at 6:58 am

    What type of assumption do we have to make over here?

  • Puzzle Prime

    Administrator
    November 5, 2018 at 1:58 pm

    Assume that the die is fair, i.e. there is 1% chance that it lands on any of its sides. Also, the outcome of every throw is independent of the previous outcomes.

  • Vivek

    Member
    October 21, 2020 at 3:52 am

    (100/101)^100 approximates to 1/e

    • Vivek

      Member
      October 21, 2020 at 1:09 pm

      Is this right? used recurrence relation to get this.

    • Puzzle Prime

      Administrator
      October 21, 2020 at 3:18 pm

      Yeah, it seems right:) I don’t remember the original solution, but if we set F(n) = P(win after side n), we get:

      F(1) + F(2) + … + 101F(m) = 100

      for m = 1, 2, … , 100. Then, it is easy to check that F(m) = (100/101)ᵐ, and therefore F(100) = (100/101)¹⁰⁰.

      I feel there is some more elegant, combinatorial solution though, it is worth thinking about it:)

    • Vivek

      Member
      October 22, 2020 at 1:57 am

      It really is (n/(n+1))^n for n sided dice, approximating to 1/e as n increases. Confirmed it by simulating in R program. This is the nice way to see the e value with probabilistic simulation. I remember that the probability of derangement approaches 1/e. But This one is really super cool!

    • Vivek

      Member
      October 22, 2020 at 2:42 am

      Another interesting question with the interesting answer as well! What is the expected number of throws till somebody wins?

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