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I keep on throwing a fair die repeatedly till the cumulative sum reaches or crosses 100. What is the probability that the last throw was a six? This needs to be solved without asymptotic assumptions. Thanks a lot!

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  • $\begingroup$ You might get some useful ideas from the closely related thread at stats.stackexchange.com/questions/145621. $\endgroup$
    – whuber
    Commented Jul 27, 2017 at 23:39
  • $\begingroup$ Whuber, thanks for your suggestion. So, it seems we cannot find a closed-form solution without assuming 100 to be a large number, right? That was where I got stuck, and posted this in the first place. $\endgroup$ Commented Jul 28, 2017 at 20:59
  • $\begingroup$ That thread shows just the opposite: it explains how you can compute the value exactly and shows why it will be very close to $2/7$. Indeed, the answer is a rational number which, in reduced form, is a quotient of two 71-digit numbers and is about 4e-15 less than $2/7$. $\endgroup$
    – whuber
    Commented Jul 28, 2017 at 22:22

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