In a town, 25% of families own a phone and 15% own a car; 65% own neither. Exactly 2000 families own both a phone and a car. Consider the statements: (i) 10% own both, (ii) 35% own either a car or a phone, (iii) 40,000 families live in the town. Which statements are correct?

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:

  • % with phone = 25.
  • % with car = 15.
  • % with neither = 65 ⇒ % with either = 35.
  • Families owning both = 2000.


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:

Either = 100% − 65% = 35% ⇒ Statement (ii) is true.25% + 15% − both% = 35% ⇒ both% = 5% (not 10%) ⇒ Statement (i) is false.5% corresponds to 2000 families ⇒ Total families = 2000 / 0.05 = 40,000 ⇒ Statement (iii) is true.


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

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