Minimum probability of winning a bet

gamblingprobability

I have the below scenario.

Suppose you are playing a game where you and your opponent have put
$\$10$ in the pot each. Your opponent bets another $\$10$. What is the
minimum probability of you winning to call this $\$10$ bet?

Attempt

There is $\$30$ in the pot: $\$20$ from the opponent and $\$10$ from me. If I call, I increase the pot to $\$40$ and the game continues. Is the minimum probability $10/30=1/3$? This is the ratio of my risk to reward before I decide to call.

Best Answer

Suppose that we win nothing if we do not call. Let $p$ be our probability of winning. Then when we call the expectation of our gain is $$(30p-10(1-p))\$=(40p-10)\$ .$$ So when $p>1/4$ the expectation is a positive number of dollars.

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