Difficulty: Medium
Correct Answer: II and III
Explanation:
Introduction / Context:
This is an inclusion–exclusion application coupled with converting counts to percentages. The ”neither” percent gives ”either” directly, and the given counts anchor the town’s population.
Given Data / Assumptions:
Concept / Approach:
Use inclusion–exclusion: P(phone ∪ car) = P(phone) + P(car) − P(both). Since 65% own neither, P(phone ∪ car) = 35%. Plug known phone and car percentages to get P(both). Then use the 2000 count to find total families.
Step-by-Step Solution:
Verification / Alternative check:
Check: 25 + 15 − 5 = 35% aligns with ”either,” consistent with 65% ”neither.”
Why Other Options Are Wrong:
Any option including (i) is invalid since both% is 5%, not 10%. ”Only II” omits the correct (iii).
Common Pitfalls:
Mixing ”either” with ”exactly one,” or forgetting that ”neither” immediately gives ”either.”
Final Answer:
II and III
Discussion & Comments