Prashant SirSSC previous year questions, solved

General Intelligence and Reasoning / Number Series

SSC CGL 2023 · tier 1 shift 3 · question 14

Select the number that will come next in the given series. 2, 5, 11, 23, 47, ?

दी गई श्रृंखला में अगली संख्या चुनिए। 2, 5, 11, 23, 47, ?

  1. a93
  2. b94
  3. c95
  4. d96

Answer: (c) 95

Why this is the answer

Each term is the previous term multiplied by 2 and increased by 1: 2×2+1 = 5, 5×2+1 = 11, 11×2+1 = 23, 23×2+1 = 47. So the next term is 47×2+1 = 95.

प्रत्येक पद पिछले पद को 2 से गुणा करके 1 जोड़ने पर प्राप्त होता है: 2×2+1 = 5, 5×2+1 = 11, 11×2+1 = 23, 23×2+1 = 47। अतः अगला पद 47×2+1 = 95 होगा।

Why the other options are wrong

  • (a) 93This is 47 × 2 - 1, which does not match the pattern of the earlier terms.

    यह 47 × 2 - 1 है, जो पूर्ववर्ती पदों के pattern से मेल नहीं खाता।

  • (b) 94This is simply 47 doubled, leaving out the +1 that each step adds.

    यह केवल 47 का दोगुना है, जिसमें प्रत्येक चरण में जुड़ने वाला +1 छूट गया है।

  • (d) 96This adds 2 instead of 1 after doubling, which no earlier step does.

    इसमें दोगुना करने के बाद 1 के स्थान पर 2 जोड़ा गया है, जो किसी पूर्व चरण में नहीं हुआ।

Explained by Prashant Solanki, SSC CPO — All India Rank 29.

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