Dice Sums Probability
1. **Stating the problem:**
We roll two six-sided balanced dice. We want to find the probabilities of:
i. Sum equals 8
ii. Sum equals 6 or 9
iii. Sum equals 3, 8, or 12
iv. Sum is not an even number
2. **Total number of outcomes:**
Each die has 6 faces, so total outcomes when rolling two dice are $$6 \times 6 = 36$$.
3. **Sum equals 8:**
Possible pairs that sum to 8 are: (2,6), (3,5), (4,4), (5,3), (6,2). There are 5 such pairs.
Probability $$P(8) = \frac{5}{36}$$.
4. **Sum equals 6 or 9:**
Pairs summing to 6: (1,5), (2,4), (3,3), (4,2), (5,1) → 5 pairs.
Pairs summing to 9: (3,6), (4,5), (5,4), (6,3) → 4 pairs.
Total pairs = 5 + 4 = 9.
Probability $$P(6 \text{ or } 9) = \frac{9}{36} = \frac{1}{4}$$.
5. **Sum equals 3, 8, or 12:**
Sum 3: (1,2), (2,1) → 2 pairs.
Sum 8: 5 pairs (from step 3).
Sum 12: (6,6) → 1 pair.
Total pairs = 2 + 5 + 1 = 8.
Probability $$P(3,8,\text{or}\ 12) = \frac{8}{36} = \frac{2}{9}$$.
6. **Sum is not an even number:**
Check sums that are odd: 3, 5, 7, 9, 11.
Count pairs for each:
- 3: 2 pairs
- 5: (1,4), (2,3), (3,2), (4,1) → 4 pairs
- 7: (1,6), (2,5), (3,4), (4,3), (5,2), (6,1) → 6 pairs
- 9: 4 pairs (from step 4)
- 11: (5,6), (6,5) → 2 pairs
Total odd sum pairs = 2 + 4 + 6 + 4 + 2 = 18.
Probability $$P(\text{not even}) = \frac{18}{36} = \frac{1}{2}$$.
**Final answers:**
i. $$\frac{5}{36}$$
ii. $$\frac{1}{4}$$
iii. $$\frac{2}{9}$$
iv. $$\frac{1}{2}$$