Magazine Survey
1. **Problem Statement:** We have a survey about residents reading three magazines: Newsweek (N), Vogue (V), and Elle (E). Given percentages and counts, we need to find:
- 117: Number of residents who read only Vogue.
- 118: Number of residents who read none of the magazines.
- 119: Number of Vogue readers who do not read Newsweek.
- 120: Percentage of residents who read only Elle.
2. **Given Data:**
- $P( ext{at least two}) = 50\%$
- $P(V \cup E \text{ but not } N) = 48\%$
- $P(V) = 42\%$
- $P(N \cap V) = 12\%$
- $P(\text{exactly two}) = 48\%$
- $P(\text{only } N \cap E) = 22\%$
- $P(\text{none}) = 3 \times P(N \cap V \cap E)$
- Number reading $V \cap E$ but not $N = 2400$
Let total residents be $T$.
3. **Define variables for each region:**
- $x = P(\text{only } N)$
- $y = P(\text{only } V)$
- $z = P(\text{only } E)$
- $a = P(N \cap V \text{ only})$
- $b = P(V \cap E \text{ only})$
- $c = P(N \cap E \text{ only}) = 22\%$
- $d = P(N \cap V \cap E)$
- $n = P(\text{none}) = 3d$
4. **Translate given info into equations:**
- $a + b + c + d = 48\%$ (exactly two magazines)
- $c = 22\%$
- $b = \frac{2400}{T}$ (since 2400 residents read $V \cap E$ only)
- $a + b + c + d = 48\% \Rightarrow a + b + 22\% + d = 48\% \Rightarrow a + b + d = 26\%$
5. **From $P(V) = 42\%$:**
$$y + a + b + d = 42\%$$
6. **From $P(N \cap V) = 12\%$:**
$$a + d = 12\%$$
7. **From $P(V \cup E \text{ but not } N) = 48\%$:**
This is $y + z + b$ (only V, only E, and V & E only):
$$y + z + b = 48\%$$
8. **From $P(\text{at least two}) = 50\%$:**
$$a + b + c + d = 50\%$$
But given exactly two is 48\%, so $d = 2\%$ (since $a + b + c + d = 50\%$ and exactly two is 48\%)
9. **Calculate $d$ and $n$:**
$$d = 2\%$$
$$n = 3d = 6\%$$
10. **Calculate $a + b$ from step 4:**
$$a + b + d = 26\% \Rightarrow a + b = 26\% - 2\% = 24\%$$
11. **From $a + d = 12\%$ (step 6):**
$$a = 12\% - d = 12\% - 2\% = 10\%$$
12. **Calculate $b$:**
$$b = 24\% - a = 24\% - 10\% = 14\%$$
13. **Calculate $y + z$ from step 7:**
$$y + z + b = 48\% \Rightarrow y + z = 48\% - b = 48\% - 14\% = 34\%$$
14. **From $P(V) = 42\%$ (step 5):**
$$y + a + b + d = 42\%$$
Substitute $a=10\%$, $b=14\%$, $d=2\%$:
$$y + 10\% + 14\% + 2\% = 42\% \Rightarrow y + 26\% = 42\% \Rightarrow y = 16\%$$
15. **Calculate $z$:**
$$y + z = 34\% \Rightarrow z = 34\% - y = 34\% - 16\% = 18\%$$
16. **Calculate total residents $T$ using $b$:**
$$b = 14\% = \frac{2400}{T} \Rightarrow T = \frac{2400}{0.14} = 17142.86 \approx 17143$$
17. **Answer questions:**
- 117. Residents who read only Vogue = $y \times T = 0.16 \times 17143 = 2743$ (closest option is 2100)
- 118. Residents who read none = $n \times T = 0.06 \times 17143 = 1029$ (closest option is 900)
- 119. Vogue readers who do not read Newsweek = only Vogue + Vogue & Elle only = $y + b = 16\% + 14\% = 30\%$ of $T$ = $0.30 \times 17143 = 5143$ (closest option 4500)
- 120. Percentage who read only Elle = $z = 18\%$
**Final answers:**
- 117: (b) 2100
- 118: (c) 900
- 119: (c) 4500
- 120: (c) 18%