1. **State the problem:**
We have a game where an eight-sided die (values 1 to 8) is rolled.
If the number rolled is a multiple of 3, the player wins double the amount rolled.
Otherwise, the player loses the amount rolled.
2. **Define the random variable and expected value formula:**
Let $X$ be the amount won or lost.
The expected value $E(X)$ is given by:
$$E(X) = \sum (\text{value} \times \text{probability})$$
3. **Identify multiples of 3 on the die:**
Multiples of 3 between 1 and 8 are 3 and 6.
4. **Calculate the value of $X$ for each outcome:**
- For 3 and 6: win double the amount rolled, so $X = 2 \times 3 = 6$ and $X = 2 \times 6 = 12$ respectively.
- For other numbers (1, 2, 4, 5, 7, 8): lose the amount rolled, so $X = -1, -2, -4, -5, -7, -8$ respectively.
5. **Calculate the expected value:**
Each outcome has probability $\frac{1}{8}$.
$$E(X) = \frac{1}{8}(6 + 12 - 1 - 2 - 4 - 5 - 7 - 8)$$
6. **Simplify inside the parentheses:**
$$6 + 12 = 18$$
$$-1 - 2 - 4 - 5 - 7 - 8 = -(1 + 2 + 4 + 5 + 7 + 8) = -27$$
So,
$$E(X) = \frac{1}{8}(18 - 27) = \frac{1}{8}(-9)$$
7. **Final expected value:**
$$E(X) = -\frac{9}{8} = -1.125$$
**Interpretation:** On average, the player loses 1.125 units per game played.
Expected Value Die 0805Da
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