What are the odds of it?

In this universe the chances of getting struck by lightning is 1/145289,

n is the number of rock paper scissors games won in a row (If the players draw they redo) required to match the chance of getting struck by lightning.

What is n (rounded down)


The answer is 17.

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1 solution

Jordan Cahn
Feb 4, 2019

Let p p be the probability of winning a given Rock Paper Scissors game. Then p = 1 3 Probability you win immediately + 1 3 p Probability you win after drawing 2 3 p = 1 3 p = 1 2 \begin{aligned} p &= \overbrace{\frac{1}{3}}^{\color{#3D99F6}\text{Probability you win immediately}} + \overbrace{\frac{1}{3}p}^{\color{#3D99F6}\text{Probability you win after drawing}}\\ \frac{2}{3} p &= \frac{1}{3} \\ p &= \frac{1}{2} \end{aligned}

Now, we solve p n = 1 145289 1 2 n = 1 145289 2 n = 145289 n 17.15 \begin{aligned} p^n &= \frac{1}{145289} \\ \frac{1}{2^n} &= \frac{1}{145289} \\ 2^n &= 145289 \\ n &\approx 17.15 \end{aligned}

Thus n = 17 \lfloor n\rfloor = \boxed{17} .

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