Key facts

  • Square, cube, prime and position-based patterns use familiar landmarks such as n^2, n^3, prime numbers, n(n + 1), or small adjustments around those va...
  • Mixed series often alternate between two independent tracks, such as positions 1, 3, 5 and positions 2, 4, 6;
  • Power-based and logarithm-adjacent patterns often use 2^n, 3^n, 10^n, square roots or simple inverse steps;

Key Points at a Glance

  1. 1

    Arithmetic series use a constant difference: each next term equals the previous term plus d; if first differences are not constant, check second-level differences before changing the rule family.

  2. 2

    Geometric series use a constant ratio: each next term equals the previous term multiplied or divided by the same value; confirm the ratio across all adjacent terms.

  3. 3

    Square, cube, prime and position-based patterns use familiar landmarks such as n^2, n^3, prime numbers, n(n + 1), or small adjustments around those values.

  4. 4

    Mixed series often alternate between two independent tracks, such as positions 1, 3, 5 and positions 2, 4, 6; split the positions before forcing one common rule.

  5. 5

    Wrong-term questions need the same rule to fit every correct term; do not change the last term merely because it is easiest to notice.

  6. 6

    Quadratic-difference series use steadily changing first differences; when the first differences rise by a constant amount, the second difference gives the rule.

  7. 7

    Power-based and logarithm-adjacent patterns often use 2^n, 3^n, 10^n, square roots or simple inverse steps; verify the landmark sequence before applying any adjustment.

  8. 8

    For CET speed, test difference, ratio, second difference, square or cube landmarks, position rules and alternate tracks in a fixed order before moving to heavier patterns.

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What the topic tests

Number series is directly in scope for CET Graduation 2026 under the official "Logical reasoning & Mathematics" block through the listed bullet "Number Series." The candidate is not expected to memorise hundreds of ready-made tricks. The real skill is to test a proposed rule against every visible term, reject coincidence, and identify the value or wrong term that keeps the whole linear pattern consistent. At graduation level, the arithmetic remains school-level, but the presentation can be wider: mixed patterns, alternate tracks, second differences, powers, position-based rules and less direct signalling of the operation.

The topic also tests speed discipline. A candidate who jumps at the first visible pattern may get trapped by a partial rule, especially when alternate terms or second differences are involved. A candidate who over-searches may waste time on an easy arithmetic series. The practical balance is to start with common checks, move to structured checks, and stop when the evidence is enough.

Core idea: treat every answer as a rule that must explain the whole visible series, not just one blank.

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