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In this problem, it is said that you and a friend are playing cards, you make a friendly wager.
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The bet is that you will draw two cards without replacement from a standard deck of cards.
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If both of the cards are diamonds, your friend will pay you $256.
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Otherwise, you need to pay your friend a total of $14.
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We have been asked to determine the expected value of this bet.
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So if we consider x to be the random variable denoting the amount of money you make, then we want to find the expected value of this random variable.
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The formula for this is summation x times p of x, where x represents the values that x can take and p of x represents the corresponding probabilities.
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So first of all, consider the case in which you select two cards so that both are diamonds.
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In this case, your friend will pay you $256, so you gain $256 and so x is 256.
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The corresponding probability is the probability that you select two cards so that both of them are diamonds.
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So this will be the number of favorable outcomes divided by the total number of outcomes.
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What's the total number of outcomes? well, out of the 52 cards in a standard deck of cards, you select any two at random.
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We can do this in 52 c2 ways...