Coin Probabilities
1. **Problem statement:** We toss a fair coin 3 times.
(1) Find the probability of exactly 2 heads.
(2) Find the probability of more than 1 tail.
(3) Find the probability of all heads.
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2. **Understanding the problem:**
Each coin toss has 2 possible outcomes: Heads (H) or Tails (T).
Total number of possible outcomes in 3 tosses is $$2^3 = 8$$.
3. **Step 1: Probability of exactly 2 heads.**
Number of ways to get exactly 2 heads out of 3 tosses is the binomial coefficient $$\binom{3}{2}$$.
Calculate:
$$\binom{3}{2} = \frac{3!}{2!(3-2)!} = \frac{3 \times 2 \times 1}{2 \times 1 \times 1} = 3$$
Probability is number of favorable outcomes over total outcomes:
$$P(\text{exactly 2 heads}) = \frac{3}{8}$$
4. **Step 2: Probability of more than 1 tail.**
More than 1 tail means 2 or 3 tails.
Calculate ways:
- Exactly 2 tails: $$\binom{3}{2} = 3$$
- Exactly 3 tails: $$\binom{3}{3} = 1$$
Total favorable outcomes = $$3 + 1 = 4$$
Probability:
$$P(\text{more than 1 tail}) = \frac{4}{8} = \frac{1}{2}$$
5. **Step 3: Probability of all heads.**
There's only 1 way to get all heads: HHH.
Probability:
$$P(\text{all heads}) = \frac{1}{8}$$
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**Final answers:**
(1) $$\frac{3}{8}$$
(2) $$\frac{1}{2}$$
(3) $$\frac{1}{8}$$