Venn Diagram Problems
1. Problem 1: Given the numbers of students in various subject combinations, find the following using a Venn diagram for Nursing (N), Business (B), and Computer (C).
2. i. All three subjects: Given as 17 (Nursing and Business and Computer).
3. ii. Business or Nursing but not Computer: This means students in B or N excluding those in C.
4. iii. Business and Nursing but not Computer: Given as 50 (Nursing and Business) minus those in all three (17), so $50 - 17 = 33$.
5. iv. At least two subjects: Sum of students in exactly two subjects plus those in all three.
6. Exactly two subjects are:
- Nursing and Business but not Computer: 33
- Business and Computer but not Nursing: $18 - 17 = 1$
- Computer and Nursing but not Business: $19 - 17 = 2$
7. So, at least two subjects = $33 + 1 + 2 + 17 = 53$.
8. v. At most two subjects: Total students minus those in all three subjects.
9. Total students = Nursing + Business + Computer - (sum of exactly two subjects) - 2 * (all three subjects) + (all three subjects)
10. Using inclusion-exclusion:
$$N + B + C - (N \cap B + B \cap C + C \cap N) + (N \cap B \cap C)$$
$$= (Nursing) + (Business) + (Computer) - (50 + 18 + 19) + 17$$
11. But we need total students first. Since the problem does not give total, we assume total is the union of all three sets.
12. vi. Exactly two subjects: Sum of students in exactly two subjects = $33 + 1 + 2 = 36$.
13. Problem 2: Given a Venn diagram with sets P, Q, and R, and values labeled including $x$, find:
14. i. Find $x$ such that $n(P) = 87$.
15. From the diagram, $n(P) = x + (x + 3) + (2x + 4) = 87$.
16. Simplify:
$$x + x + 3 + 2x + 4 = 87$$
$$4x + 7 = 87$$
$$4x = 80$$
$$x = 20$$
17. ii. $n$ is not fully specified; assuming it means total number of elements in the universal set, sum all parts:
18. $n = n(P \cup Q \cup R) = n(P) + n(Q) + n(R) - n(P \cap Q) - n(Q \cap R) - n(P \cap R) + n(P \cap Q \cap R)$
19. Using values:
- $n(P) = 87$
- $n(Q) = 18 + x = 18 + 20 = 38$
- $n(R)$ parts: $x + 3 = 23$, plus other parts unknown, so insufficient data to find total.
20. iii. $(R)'$ is the complement of $R$, meaning elements not in $R$. Without total universal set size, cannot find exact number.
21. iv. $n(R \cup Q)$ is the number of elements in $R$ or $Q$ or both.
22. v. $n(P \cap Q)'$ is the complement of the intersection of $P$ and $Q$.
23. vi. Probability of $n(R)$ is $\frac{n(R)}{n(U)}$, where $n(U)$ is total elements in universal set.
24. Without total universal set size, exact numerical answers for parts ii, iii, iv, v, and vi cannot be determined.
Final answers:
- Problem 1:
i. All three subjects = 17
ii. Business or Nursing but not Computer = (Nursing + Business) - (all three + Business and Computer + Nursing and Computer) = $50 + ? - (17 + 18 + 19)$ but incomplete data for exact number.
iii. Business and Nursing but not Computer = 33
iv. At least two subjects = 53
v. At most two subjects = Total - 17 (all three subjects)
vi. Exactly two subjects = 36
- Problem 2:
i. $x = 20$
"slug":"venn diagram problems","subject":"set theory","desmos":{"latex":"","features":{"intercepts":false,"extrema":false}},"q_count":2