Meal Booking Probability
1. **State the problem:** We have 71 guests with bookings involving breakfast (B), lunch (L), and supper (S). We need to find probabilities related to meal bookings based on the Venn diagram data.
2. **Identify given data from the Venn diagram:**
- Only B: 24
- Only L: 9
- Only S: 16
- B and L only: 6
- B and S only: 7
- L and S only: 5
- All three (B, L, S): 3
- Total guests: 71
3. **Calculate total guests who booked all three meals:** 3
4. **Calculate guests who have not booked all three meals:**
$$71 - 3 = 68$$
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**Part a i:** Find the probability that a guest who has not booked all three meals has booked breakfast or supper.
5. Calculate number of guests who booked breakfast or supper but not all three:
- Breakfast only: 24
- Supper only: 16
- B and L only: 6 (includes B)
- B and S only: 7 (includes B and S)
- L and S only: 5 (includes S)
- Exclude all three: 3
Guests with breakfast or supper (excluding all three):
$$24 + 16 + 6 + 7 + 5 = 58$$
6. Probability:
$$P = \frac{58}{68} = \frac{29}{34} \approx 0.8529$$
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**Part a ii:** Find the probability that a guest has not booked supper given that they have booked lunch.
7. Calculate guests who booked lunch:
- Only L: 9
- B and L only: 6
- L and S only: 5
- All three: 3
Total lunch bookings:
$$9 + 6 + 5 + 3 = 23$$
8. Calculate guests who booked lunch but not supper:
- Only L: 9
- B and L only: 6
Total lunch but no supper:
$$9 + 6 = 15$$
9. Conditional probability:
$$P(\text{no supper} | L) = \frac{15}{23} \approx 0.6522$$
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**Part b:** Find the probability that two randomly selected guests both booked lunch given that both booked at least two meals.
10. Calculate guests who booked at least two meals:
- B and L only: 6
- B and S only: 7
- L and S only: 5
- All three: 3
Total at least two meals:
$$6 + 7 + 5 + 3 = 21$$
11. Calculate guests who booked lunch and at least two meals:
- B and L only: 6
- L and S only: 5
- All three: 3
Total lunch and at least two meals:
$$6 + 5 + 3 = 14$$
12. Probability a randomly selected guest booked lunch given at least two meals:
$$P(L | \geq 2) = \frac{14}{21} = \frac{2}{3}$$
13. Probability that two randomly selected guests both booked lunch given both booked at least two meals:
Assuming independence:
$$P = \left(\frac{2}{3}\right)^2 = \frac{4}{9} \approx 0.4444$$
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**Final answers:**
- a i: $\frac{29}{34}$
- a ii: $\frac{15}{23}$
- b: $\frac{4}{9}$