Frequency Tree Probs
1. For the lunch and gift shop problem, state given info:
- Students brought packed lunch: 43
- Students visited gift shop: 14
- Students neither brought lunch nor visited gift shop: 22
2. Let the number who brought lunch and visited gift shop be $x$.
3. Then, those who brought lunch but did not visit gift shop are $43 - x$.
4. Those who did not bring lunch but visited gift shop are $14 - x$.
5. Students who neither brought lunch nor visited gift shop = 22 (given).
6. Total students = (brought lunch and visited) + (brought lunch, no visit) + (no lunch, visited) + (neither) = $x + (43-x) + (14-x) + 22 = 43 + 14 + 22 - x = 79 - x$.
7. This total should equal total students, so $79 - x$ is total.
8. Since number can't be negative, $x$ must be such that each branch count is nonnegative.
9. Usually $x$ is given or assumed to be the intersection of lunch and visit counts; use the principle of inclusion-exclusion:
$$\text{Total} = |L| + |G| - |L \cap G| + |\text{neither}|\Rightarrow \text{Total} = 43 + 14 - x + 22$$
So $\text{Total} = 79 - x$ as above.
10. The problem does not give total students, so find $x$ consistent with total students:
- Sum all must equal total = $T$.
- Total equals $79 - x$.
11. The question is: How many students brought packed lunch and did not visit gift shop?
That's $43 - x$.
12. Without total $T$ or additional constraints, cannot find exact $x$, but using minimal overlap assumption for maximum $x$, assume $x = 14$ (all who visited gift shop also brought lunch).
13. Then packed lunch and no visit: $43 - 14 = 29$.
14. For the Spanish and French test problem:
- Pass Spanish & Pass French = 14
- Pass Spanish & Fail French = 12
- Fail Spanish total = 24, of which Pass French = 9, Fail French = $24 - 9 = 15$
15. Total students = sum all outcomes = $14 + 12 + 9 + 15 = 50$.
16. Probability student failed at least one test = 1 - probability passed both.
17. Probability passed both tests = $\frac{14}{50} = \frac{7}{25}$.
18. Therefore, probability failed at least one test = $1 - \frac{7}{25} = \frac{18}{25}$.
Final answers:
- Students who brought packed lunch and did not visit gift shop: 29
- Probability failed at least one test: $\frac{18}{25}$