1. **State the problem:** You pay 2 dollars to play a game where a fair six-sided die is rolled. You receive a payout equal to the number of dots on the die face. The net gain is the payout minus the 2 dollars paid.
2. **Formula for expected value:** The expected value $E$ of the net gain is given by
$$E = \sum (\text{net gain} \times \text{probability})$$
3. **Calculate net gains for each outcome:**
- If the die shows 1, net gain = $1 - 2 = -1$
- If the die shows 2, net gain = $2 - 2 = 0$
- If the die shows 3, net gain = $3 - 2 = 1$
- If the die shows 4, net gain = $4 - 2 = 2$
- If the die shows 5, net gain = $5 - 2 = 3$
- If the die shows 6, net gain = $6 - 2 = 4$
4. **Calculate expected value:**
Since the die is fair, each outcome has probability $\frac{1}{6}$.
$$E = \frac{1}{6}(-1) + \frac{1}{6}(0) + \frac{1}{6}(1) + \frac{1}{6}(2) + \frac{1}{6}(3) + \frac{1}{6}(4)$$
5. **Simplify:**
$$E = \frac{-1 + 0 + 1 + 2 + 3 + 4}{6} = \frac{9}{6} = 1.5$$
6. **Interpretation:** The expected net gain is $1.5$. Since you pay 2 dollars to play, on average you gain 1.5 dollars net, so the game is favorable to the player and not fair (fair would mean expected net gain of 0).
Expected Value Die 87D9F5
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