A digit n > 3 is divisible by 3 but not divisible by 6. Which one of the following is divisible by 4?
Answer & explanation
Answer: (d) 3n + 1
The digits greater than 3 that are divisible by 3 are 6 and 9; 6 is divisible by 6, so n = 9. Then 3n + 1 = 28 is the only option divisible by 4.
- Digits above 3 divisible by 3: 6 and 9. 6 is divisible by 6, so n = 9.
- 2n = 18, 3n = 27, 2n + 4 = 22 — none divisible by 4.
- 3n + 1 = 28 = 4 × 7 — divisible by 4.
Remember · When a condition pins a single digit, find that digit first and then test every option numerically.
Question and answer: UPSC's official GS Paper II (2020, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·