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A deck of cards contains 52 cards, of which 4 are aces. You are offered the following wager: Draw one card at random from the deck. You win \(\$ 10\) if the card drawn is an ace. Otherwise, you lose \(\$ 1\). If you make this wager very many times, what will be the mean amount you win? (a) About \(-\$ 1\), because you will lose most of the time. (b) About \(\$ 9,\) because you win \(\$ 10\) but lose only \(\$ 1\). (c) About \(-\$ 0.15\); that is, on average you lose about 15 cents. (d) About \(\$ 0.77 ;\) that is, on average you win about 77 cents. (e) About \(\$ 0,\) because the random draw gives you a fair bet.

Short Answer

Expert verified
(c) About -$0.15; you lose about 15 cents on average.

Step by step solution

01

Determine the Probabilities

First, calculate the probability of drawing an ace from the deck. Since there are 4 aces in a deck of 52 cards, the probability is \( P(A) = \frac{4}{52} = \frac{1}{13} \). The probability of not drawing an ace, therefore, is \( P(A^c) = 1 - \frac{1}{13} = \frac{12}{13} \).
02

Calculate Expected Value for Winning

For drawing an ace, you win \( \$10 \). The expected value for this event is calculated as: \[ E_{\text{win}} = \frac{1}{13} \times 10 = \frac{10}{13} \approx 0.77 \].
03

Calculate Expected Value for Losing

For any card that isn't an ace, you lose \( \$1 \). Thus, the expected value for this event is: \[ E_{\text{lose}} = \frac{12}{13} \times (-1) = -\frac{12}{13} \approx -0.92 \].
04

Calculate Total Expected Value

The mean amount you expect to win (the expected value of the wager) is the sum of the expected winning and losing: \[ E = E_{\text{win}} + E_{\text{lose}} = \frac{10}{13} - \frac{12}{13} = -\frac{2}{13} \approx -0.15 \].
05

Conclusion

After calculating, you expect to lose about \( \$0.15 \) on average per draw. Thus, the correct answer is (c).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Expected Value
The concept of expected value is fundamental in probability and helps us anticipate the average outcome of a random event over the long run. Imagine doing an activity repeatedly, like flipping a coin or, in our case, drawing cards.

In our card drawing scenario, the expected value tells us about the average cash win or loss over many rounds. To find it, multiply each possible outcome by its probability, and sum these results.

Let's break it down for clarity:
  • You can win \(10 with a probability of drawing an ace, \( \frac{1}{13} \).
  • Or lose \)1 with the probability of not drawing an ace, \( \frac{12}{13} \).
The expected value becomes the assembled total of these possibilities, equaling roughly -0.15 dollars per card drawn—indicating, on average, a small loss per game.
Card Games
Card games are fascinating due to their blend of luck, strategy, and probability. A standard deck of 52 cards, like in our exercise, forms the basis of countless games and scenarios.

Here's a short overview of the deck:
  • 52 cards in total.
  • Divided into four suits: hearts, diamonds, clubs, and spades.
  • Each suit contains 13 cards, including one ace, both adding up to four aces in a deck, crucial for our wager task.
Understanding these basics allows you to calculate probabilities and expected values in games. Knowing how many possible events exist, like drawing an ace, helps you estimate outcomes and strategize your moves effectively.

Whether you're playing poker or making a wager like in the exercise, these foundational elements are essential.
Probability of Events
When we talk about probability, we refer to the chance of an event happening. It's usually a fraction between 0 (impossible) to 1 (certain). For a card game, every draw changes the opportunity of pulling a specific card, like drawing one of the four aces.

Calculating probabilities involves:
  • Counting the desired outcomes (e.g., 4 aces).
  • Dividing by the total number of possible outcomes (e.g., 52 cards).
This gives us \( \frac{4}{52} = \frac{1}{13} \) for drawing an ace. The chance of not drawing an ace is simply the complement, \( \frac{12}{13} \).

Probabilities are foundational in predicting expected outcomes, such as whether to expect profit or loss in gambling scenarios. By understanding and calculating the probability of events, you can make more informed decisions, like determining if a card wager is in your favor.

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