A survey of readers — Caselets Aptitude Question
A survey of readers: In a survey of 500 people, 280 read newspaper A, 220 read newspaper B, and 90 read both. Answer and worked solution on CodeKairo.
- Topic: Caselets
- Section: Data Interpretation
- Difficulty: Medium
- Time target: 75 seconds
Question
In a survey of 500 people, 280 read newspaper A, 220 read newspaper B, and 90 read both.
How many read neither newspaper?
Options
- 80
- 90
- 100
- 110
Show the answer and the worked solution
Correct answer: B. 90
Worked solution
- At least one = 280 + 220 − 90 = 410.
- Neither = 500 − 410 = 90.
Answer: 90.
The idea
Add the two groups, subtract the overlap once, then take the complement. Forgetting the overlap gives 0, which is impossible.
Shortcut. 280 + 220 is exactly 500, so the 90 counted twice must equal the number counted zero times: neither = both = 90.
Common trap. 100 is the tempting round figure, but it needs exactly 400 readers of at least one paper; 280 + 220 − 90 = 410, leaving 90.