What is X in the sequence 132, 129, 124, 117, 106, 93, X?
Answer & explanation
Answer: (c) 76
The terms fall by 3, 5, 7, 11 and 13 — consecutive primes. The next prime is 17, so X = 93 − 17 = 76.
- Differences: 132 − 129 = 3, 129 − 124 = 5, 124 − 117 = 7, 117 − 106 = 11, 106 − 93 = 13.
- These are consecutive primes; the next one is 17.
- X = 93 − 17 = 76.
Remember · When differences grow irregularly, test primes, squares and cubes first.
Question and answer: UPSC's official GS Paper II (2019, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·