अनुक्रम 20, 10, 10, 15, 30, 75, X में X का मान क्या है?
Read this question in English
What is the value of X in the sequence 20, 10, 10, 15, 30, 75, X?
(a) 105 · (b) 120 · (c) 150 · (d) 225
उत्तर और व्याख्या · explanation in English
Answer: (d) 225
Each term is the previous one multiplied by a factor that grows by 0.5 each time: ×0.5, ×1, ×1.5, ×2, ×2.5. The next factor is ×3, so X = 75 × 3 = 225.
- Divide each term by the one before it: 10 ÷ 20 = 0.5, 10 ÷ 10 = 1, 15 ÷ 10 = 1.5, 30 ÷ 15 = 2, 75 ÷ 30 = 2.5.
- The multiplier rises by 0.5 each time, so the next multiplier is 3.
- X = 75 × 3 = 225.
- Check: 225 ÷ 75 = 3 continues the pattern 0.5, 1, 1.5, 2, 2.5, 3.
Remember · When differences look irregular, try the ratio of consecutive terms; a steadily growing multiplier is a common pattern.
Question and answer: UPSC's official GS Paper II (2022, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·