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Odds across books

Market makingHard

Book offers decimal odds of on outcome A and on outcome B. Book offers on A and on B. Exactly one of A or B happens, and a winning bet returns stake times odds. A bettor places a total of split between A at the best odds and B at the best odds, choosing the split so that the payout is the same whichever outcome occurs. What is the guaranteed profit, rounded to decimal places?

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A whole number, a decimal, a fraction like 3/8 or a percent.

Hint

Each side's stake is the target payout divided by its odds.

Solution
  1. The best odds are on A and on B, so the stakes for a payout of S are and .
  2. Setting gives .
  3. The guaranteed profit is .

Answer: