Medium · Expected Value & Decision Theory · Numerical · ~8 min · #52

Thirty-Sided Die vs Twenty-Sided Die

Real interview · Jane Street

You roll a fair 30-sided die (result $a$ ) and your opponent rolls a fair 20-sided die (result $b$ ). If $a > b$ you win $a$ dollars; if $b \ge a$ you lose $b$ dollars.

What is your expected payoff?

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Worked solution

Give the problem an honest attempt first, then reveal the full explanation.

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