Numerical Ability · Editorial

Number sequence

Find the rule; check the next term against each option.

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Number-sequence items show a list of numbers and ask for the next term (or the missing middle term). On CSE-PPT Numerical Ability, the rule is usually arithmetic, geometric, alternating, or a simple digit/pattern trick—not a PhD-level series.

How to approach

  1. Check differences first. Constant gap → arithmetic; growing gap → maybe +2, +4, +6…
  2. Check ratios second. Multiply/divide patterns (×2, ×3, ÷2).
  3. Try alternating rules. Odd positions follow one rule; even positions follow another.
  4. Test digit play when gaps look messy. Sum of digits, reverse digits, or split two interleaved sequences.
  5. Verify the candidate on the last known step. The correct option must fit the same rule that built the given terms.

Worked example

Stem: 5, 8, 14, 23, 35, ?

  1. A.44
  2. B.48
  3. C.50
  4. D.53

Work: Differences: 8−5=3, 14−8=6, 23−14=9, 35−23=12. The gaps increase by +3 each time. Next gap = 15. Next term = 35+15 = 50. Answer: C. 50.

Common traps

  • Forcing ×2 — Assuming every sequence is doubling when differences are the real story.
  • Ignoring the last gap — Finding a cute rule that fails on the final given term.
  • Two-sequence blindness — Missing that 2, 9, 4, 16, 6, 25… is 2,4,6… interleaved with squares.
  • Sign errors — Losing a minus when the series decreases.
  • Option shopping — Picking a number that “looks close” without stating a rule.

Quick practice

  1. 81, 27, 9, 3, ?
  1. A.0 B. 1 C. 2 D. 6

Answer: B — Divide by 3 each time: 3÷3=1.

  1. 4, 5, 9, 14, 23, ?
  1. A.28 B. 37 C. 32 D. 41

Answer: B — Each term is the sum of the previous two (Fibonacci-style): 14+23=37.

Study with this product

  1. Take the free diagnostic to see if this topic is a weakness.
  2. Drill Number sequence in Practice, or use Today’s plan for short pattern bursts.
  3. Take a full mock when the app recommends one so you don’t overinvest time on one stubborn series.

Honest facts

  • This guide is a study aid, not an official CSC reviewer and not a pass promise.
  • We never invent official CSC dates, fees, or room assignments.
  • Sample stems here are original practice items for skill-building, not leaked exam content.
  • Readiness Score is a product metric — not a CSC rating prediction.

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