1. **State the problem:** We roll a six-sided die 12 times and want to find the probability of getting the number 4 exactly 5 times.
2. **Identify the distribution:** This is a binomial probability problem where each roll is a trial with two outcomes: getting a 4 (success) or not getting a 4 (failure).
3. **Formula:** The binomial probability formula is
$$P(X = k) = \binom{n}{k} p^k (1-p)^{n-k}$$
where:
- $n = 12$ (number of trials)
- $k = 5$ (number of successes)
- $p = \frac{1}{6}$ (probability of success on each trial, since one face out of six is a 4)
4. **Calculate the binomial coefficient:**
$$\binom{12}{5} = \frac{12!}{5! \times (12-5)!} = \frac{12!}{5! \times 7!} = 792$$
5. **Calculate the probability:**
$$P(X=5) = 792 \times \left(\frac{1}{6}\right)^5 \times \left(\frac{5}{6}\right)^7$$
6. **Simplify:**
- $\left(\frac{1}{6}\right)^5 = \frac{1}{7776}$
- $\left(\frac{5}{6}\right)^7 = \frac{78125}{279936}$
So,
$$P(X=5) = 792 \times \frac{1}{7776} \times \frac{78125}{279936}$$
7. **Final calculation:**
$$P(X=5) = \frac{792 \times 78125}{7776 \times 279936} \approx 0.0283$$
**Answer:** The probability of rolling a 4 exactly 5 times in 12 rolls is approximately **0.0283** or 2.83%.
Binomial Die Roll 8E1032
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