Problem 267

Billionaire

You are given a unique investment opportunity.

Starting with £1 of capital, you can choose a fixed proportion, `f`, of your capital to bet on a fair coin toss repeatedly for 1000 tosses.

Your return is double your bet for heads and you lose your bet for tails.

For example, if `f` = 1/4, for the first toss you bet
£0.25, and if heads comes up you win £0.5 and so then have £1.5. You
then bet £0.375 and if the second toss is tails, you have £1.125.

Choosing `f` to maximize your chances of having at least £1,000,000,000 after 1,000 flips, what is the chance that you become a billionaire?

All computations are assumed to be exact (no rounding), but give your answer rounded to 12 digits behind the decimal point in the form 0.abcdefghijkl.

**
These problems are part of
Project Euler
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CC BY-NC-SA 2.0 UK
**