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SSC CGL Reasoning · Classification

Letter Classification

Change each letter to its place in the alphabet, then compare the clusters: equal steps, letters in a run, or letters that are opposites of each other.

All Classification notes

Why this matters

Twenty questions in the bank, 13 EASY and 7 MODERATE, twelve of them from the 2023 shifts. Every letter question in the chapter, here and on the next two pages, starts from the same habit: turning letters into numbers in a second or two.

Concept 1 of 2: Letter positions and clusters with equal steps

A letter cluster is a short number series in disguise. Once each letter is its position (A is 1, Z is 26), the rule is a step you can count.

Definition

  • Forward positions: A1 to Z26. Anchor them with EJOTY: E5, J10, O15, T20, Y25, and count one or two from the nearest anchor (R is T20 minus 2, so 18).
  • Reverse position (counting from Z): 27 minus the forward position. Z is 1, A is 26, H is 19.
  • Wrap round: after Z, carry on from A. A position above 26 loses 26 (X24 + 4 is 28, which is B2). Before A, add 26.
  • Write the steps between neighbouring letters (+3, +3). Three clusters share the step list; the odd one has a different step somewhere.
  • Letters in a plain run (BCD, RST) and the same run backwards (ONM) count as different patterns: direction matters.

Reverse position and wrapping round

reverse position=27−positionposition after Z=position−26\text{reverse position} = 27 - \text{position} \qquad \text{position after Z} = \text{position} - 26

Worked example

Find the odd one out: (a) BHN (b) EKQ (c) TZF (d) DJO
Practice this conceptself-check · 4 quick reps

The same idea in a real exam question:

SSC CGL · 2024 · Tier I, 10 Sep 2024, Shift 1 · Q5Easy

Example 1 · Classification · Letter Classification

Four letter-clusters have been given, out of which three are alike in some manner and one is different. Select the one that is different. The odd one out is not based on the number of consonants/vowels or their position in the letter cluster

Counting the starting letter as a step

Three places after D is G (E, F, G), not F. Count the letters you move onto, not the one you start from.

Stopping at Z

The alphabet wraps round. In a +4 cluster such as PTXB, X is followed by B, four places on. Subtract 26 from any position above 26.
Drill 11 more on letter positions and clusters with equal steps

Concept 2 of 2: Opposite letters, whose positions add to 27

Fold the alphabet in half and A lands on Z, B on Y, M on N. Each pair is called opposite letters, and SSC builds whole questions on them.

Definition

  • Opposite pairs: A and Z, B and Y, C and X, D and W, E and V, F and U, G and T, H and S, I and R, J and Q, K and P, L and O, M and N.
  • Two letters are opposites when their positions add to 27. To find the opposite of a letter, take its position from 27.
  • In a cluster, test which two letters are opposites (first and second, or first and third), then find the rule for the remaining letter.
  • Like a triad of numbers, a cluster can keep one link and break the other, so check both.

Opposite letters

position(L)+position(opposite of L)=27\text{position}(L) + \text{position}(\text{opposite of } L) = 27

Worked example

Find the odd one out: (a) DWF (b) KPM (c) HSJ (d) ETG
Practice this conceptself-check · 4 quick reps

The same idea in a real exam question:

SSC CGL · 2023 · Tier I, 20 Jul 2023, Shift 2 · Q8Easy

Example 2 · Classification · Letter Classification

Three of the following four letter-clusters are alike in a certain way and one is different. Pick the odd one out.

Using 26 as the total for opposite letters

Opposite positions add to 27, because A (1) pairs with Z (26). With 26 as the total you get the letter one place off, such as U for E instead of V.
Drill 7 more on opposite letters, whose positions add to 27

Summary — formulas & gotchas at a glance

A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.

Formulas (2)

  • Letter positions and clusters with equal steps

    Reverse position and wrapping round

    reverse position=27−positionposition after Z=position−26\text{reverse position} = 27 - \text{position} \qquad \text{position after Z} = \text{position} - 26
  • Opposite letters, whose positions add to 27

    Opposite letters

    position(L)+position(opposite of L)=27\text{position}(L) + \text{position}(\text{opposite of } L) = 27

Watch out for (3)

Test yourself on Classification

20 past SSC CGL questions from this chapter, timed at 12 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.

Take the Classification chapter testDrill all 20 questions